System for temporal identifier handling for hybrid scalability

ABSTRACT

This invention relates to a method for decoding a video bitstream comprising the steps of: (a) receiving a base bitstream representative of a coded video sequence; (b) receiving at least one enhancement bitstreams representative of said coded video sequence; (c) receiving a video parameter set containing syntax elements that apply to said base bitstream and said at least one Cenhancement bitstreams where said syntax elements selectively signaling bitrate and picture rate information for said base bitstream based upon whether said base bitstream is externally signaled or internally specified.

TECHNICAL FIELD

The present disclosure relates generally to electronic devices.

BACKGROUND OF THE INVENTION Background Art

Electronic devices have become smaller and more powerful in order tomeet consumer needs and to improve portability and convenience.Consumers have become dependent upon electronic devices and have come toexpect increased functionality. Some examples of electronic devicesinclude desktop computers, laptop computers, cellular phones, smartphones, media players, integrated circuits, etc.

Some electronic devices are used for processing and displaying digitalmedia. For example, portable electronic devices now allow for digitalmedia to be consumed at almost any location where a consumer may be.Furthermore, some electronic devices may provide download or streamingof digital media content for the use and enjoyment of a consumer.

SUMMARY OF INVENTION Technical Problem

The increasing popularity of digital media has presented severalproblems. For example, efficiently representing high-quality digitalmedia for storage, transmittal and rapid playback presents severalchallenges. As can be observed from this discussion, systems and methodsthat represent digital media efficiently with improved performance maybe beneficial.

Solution to Problem

According to the present invention, A method for decoding a videobitstream comprising the steps of: (a) receiving a base bitstreamrepresentative of a coded video sequence; (b) receiving at least oneenhancement bitstreams representative of said coded video sequence; (c)receiving a video parameter set containing syntax elements that apply tosaid base bitstream and said at least one enhancement bitstreams wheresaid syntax elements selectively signaling bitrate and picture rateinformation for said base bitstream based upon whether said basebitstream is externally signaled or internally specified.

BRIEF DESCRIPTION OF DRAWINGS

The foregoing and other objectives, features, and advantages of theinvention will be more readily understood upon consideration of thefollowing detailed description of the invention, taken in conjunctionwith the accompanying drawings.

FIG. 1A is a block diagram illustrating an example of one or moreelectronic devices in which systems and methods for sending a messageand buffering a bitstream may be implemented;

FIG. 1B is another block diagram illustrating an example of one or moreelectronic devices in which systems and methods for sending a messageand buffering a bitstream may be implemented;

FIG. 2A is a block diagram illustrating one configuration of an encoder604 on an electronic device;

FIG. 2B is another block diagram illustrating one configuration of anencoder 604 on an electronic device;

FIG. 3A is a block diagram illustrating one configuration of a decoderon an electronic device;

FIG. 3B is another block diagram illustrating one configuration of adecoder on an electronic device;

FIG. 4 illustrates various components that may be utilized in atransmitting electronic device;

FIG. 5 is a block diagram illustrating various components that may beutilized in a receiving electronic device;

FIG. 6 is a block diagram illustrating one configuration of anelectronic device in which systems and methods for sending a message maybe implemented; and

FIG. 7 is a block diagram illustrating one configuration of anelectronic device in which systems and methods for buffering a bitstreammay be implemented.

FIG. 8A illustrates different NAL Unit header syntax.

FIG. 8B illustrates different NAL Unit header syntax.

FIG. 8C illustrates different NAL Unit header syntax.

FIG. 9 illustrates a general NAL Unit syntax.

FIG. 10 illustrates an existing video parameter set.

FIG. 11 illustrates existing scalability types.

FIG. 12 illustrates a base layer and enhancement layers.

FIG. 13 illustrates an exemplary picture having multiple slices.

FIG. 14 illustrates another exemplary picture having multiple slices

FIG. 15 illustrates a picture with column and row boundaries.

FIG. 16 illustrates a picture with slices.

FIG. 17 illustrates an accuess unit with a base layer, enhancementlayers, and tiles.

FIG. 18A illustrates an exemplary slide segment header syntax.

FIG. 18B illustrates an exemplary slide segment header syntax.

FIG. 18C illustrates an exemplary slide segment header syntax.

FIG. 18D illustrates an exemplary slide segment header syntax.

FIG. 19 illustrates a base layer and enhancement layers.

FIG. 20A illustrates an exemplary vps extension syntax syntax.

FIG. 20B illustrates an exemplary vps extension syntax syntax.

FIG. 21 illustrates an exemplary slice segment header syntax.

FIG. 22 illustrates an exemplary slice segment header syntax.

FIG. 23 illustrates an exemplary slice segment header syntax.

FIG. 24 illustrates an exemplary base layer and enhancement layer withpermitted relationships.

FIG. 25 illustrates an exemplary slice segment header.

FIG. 26 illustrates an exemplary vps extension syntax.

FIG. 26A illustrates an exemplary vps extension syntax.

FIG. 27 illustrates an exemplary sequence parameter set syntax.

FIG. 28 illustrates an exemplary picture parameter set syntax.

FIG. 29 illustrates temporal sub-layers within a base layer and anenhancement layer.

FIG. 30A illustrates an exemplary slice segment header syntax.

FIG. 30B illustrates an exemplary slice segment header syntax.

FIG. 30C illustrates an exemplary slice segment header syntax.

FIG. 30D illustrates an exemplary slice segment header syntax.

FIG. 31 illustrates an exemplary vps_extension syntax.

FIG. 32 illustrates vps_max_sub_layers minus1 signaling.

FIG. 33 illustrates an exemplary vps_extension syntax.

FIG. 34 illustrates vps_max_sub_layers minus1 signaling.

FIG. 35 illustrates an exemplary vps_extension syntax.

FIG. 36 illustrates vps_max_sub_layers minus1 signaling.

FIG. 37 illustrates an exemplary slice_segment_header syntax.

FIG. 38 illustrates an exemplary slice_segment_header syntax.

FIG. 39 illustrates an exemplary slice_segment_header syntax.

FIG. 40 illustrates an exemplary implementation for thelayer_present_in_au_flag[i].

FIG. 41 illustrates an exemplary implementation for thelayer_present_in_au_flag[i].

FIG. 42 illustrates an exemplary implementation for thelayer_present_in_au_flag[i].

FIG. 43 illustrates an exemplary decoding process for inter-layerreference picture set.

FIG. 44 illustrates an exemplary decoding process for inter-layerreference picture set.

FIG. 45 illustrates an exemplary decoding process for inter-layerreference picture set.

FIG. 46 illustrates an exemplary decoding process for inter-layerreference picture set.

FIG. 47. Illustrates an exemplary slice segment header.

FIG. 48 illustrates temporal sub-layers with IRAP pictures and non-IRAPpictures.

FIG. 49 illustrates another temporal sub-layers within IRAP pictures andnon-IRAP pictures.

FIG. 50 illustrates temporal sub-layers within IRAP pictures, TSApictures, STSA pictures.

FIG. 51 illustrates another temporal sub-layers within IRAP pictures,TSA pictures, STSA pictures.

FIG. 52 illustrates an exemplary portion of a VPS extension syntax.

FIG. 53 illustrates an exemplary portion of a VPS extension syntax.

FIG. 54 illustrates a layer set signaling structure.

DESCRIPTION OF EMBODIMENTS

FIG. 1A is a block diagram illustrating an example of one or moreelectronic devices 102 in which systems and methods for sending amessage and buffering a bitstream may be implemented. In this example,electronic device A 102 a and electronic device B 102 b are illustrated.However, it should be noted that one or more of the features andfunctionality described in relation to electronic device A 102 a andelectronic device B 102 b may be combined into a single electronicdevice in some configurations.

Electronic device A 102 a includes an encoder 104. The encoder 104includes a message generation module 108. Each of the elements includedwithin electronic device A 102 a (e.g., the encoder 104 and the messagegeneration module 108) may be implemented in hardware, software or acombination of both.

Electronic device A 102 a may obtain one or more input pictures 106. Insome configurations, the input picture(s) 106 may be captured onelectronic device A 102 a using an image sensor, may be retrieved frommemory and/or may be received from another electronic device.

The encoder 104 may encode the input picture(s) 106 to produce encodeddata. For example, the encoder 104 may encode a series of input pictures106 (e.g., video). In one configuration, the encoder 104 may be a HEVCencoder. The encoded data may be digital data (e.g., part of a bitstream114). The encoder 104 may generate overhead signaling based on the inputsignal.

The message generation module 108 may generate one or more messages. Forexample, the message generation module 108 may generate one or more SEImessages or other messages. For a CPB that supports operation on asub-picture level, the electronic device 102 may send sub-pictureparameters, (e.g., CPB removal delay parameter). Specifically, theelectronic device 102 (e.g., the encoder 104) may determine whether toinclude a common decoding unit CPB removal delay parameter in a picturetiming SEI message. For example, the electronic device may set a flag(e.g., common_du_cpb_removal_delay_flag) to one when the encoder 104 isincluding a common decoding unit CPB removal delay parameter (e.g.,common_du_cpb_removal_delay) in the picture timing SEI message. When thecommon decoding unit CPB removal delay parameter is included, theelectronic device may generate the common decoding unit CPB removaldelay parameter that is applicable to all decoding units in an accessunit. In other words, rather than including a decoding unit CPB removaldelay parameter for each decoding unit in an access unit, a commonparameter may apply to all decoding units in the access unit with whichthe picture timing SEI message is associated.

In contrast, when the common decoding unit CPB removal delay parameteris not to be included in the picture timing SEI message, the electronicdevice 102 may generate a separate decoding unit CPB removal delay foreach decoding unit in the access unit with which the picture timing SEImessage is associated in some configurations, electronic device A 102 amay send the message to electronic device B 102 b as part of thebitstream 114. In some configurations electronic device A 102 a may sendthe message to electronic device B 102 b by a separate transmission 110.For example, the separate transmission may not be part of the bitstream114. For instance, a picture timing SEI message or other message may besent using some out-of-band mechanism. It should be noted that, in someconfigurations, the other message may include one or more of thefeatures of a picture timing SEI message described above. Furthermore,the other message, in one or more aspects, may be utilized similarly tothe SEI message described above.

The encoder 104 (and message generation module 108, for example) mayproduce a bitstream 114. The bitstream 114 may include encoded picturedata based on the input picture(s) 106. In some configurations, thebitstream 114 may also include overhead data, such as a picture timingSEI message or other message, slice header(s), PPS(s), etc. Asadditional input pictures 106 are encoded, the bitstream 114 may includeone or more encoded pictures. For instance, the bitstream 114 mayinclude one or more encoded pictures with corresponding overhead data(e.g., a picture timing SEI message or other message).

The bitstream 114 may be provided to a decoder 112. In one example, thebitstream 114 may be transmitted to electronic device B 102 b using awired or wireless link In some cases, this may be done over a network,such as the Internet or a Local Area Network (LAN). As illustrated inFIG. 1A, the decoder 112 may be implemented on electronic device B 102 bseparately from the encoder 104 on electronic device A 102 a. However,it should be noted that the encoder 104 and decoder 112 may beimplemented on the same electronic device in some configurations. In animplementation where the encoder 104 and decoder 112 are implemented onthe same electronic device, for instance, the bitstream 114 may beprovided over a bus to the decoder 112 or stored in memory for retrievalby the decoder 112.

The decoder 112 may be implemented in hardware, software or acombination of both. In one configuration, the decoder 112 may be a HEVCdecoder. The decoder 112 may receive (e.g., obtain) the bitstream 114.The decoder 112 may generate one or more decoded pictures 118 based onthe bitstream 114. The decoded picture(s) 118 may be displayed, playedback, stored in memory and/or transmitted to another device, etc.

The decoder 112 may include a CPB 120. The CPB 120 may temporarily storeencoded pictures. The CPB 120 may use parameters found in a picturetiming SEI message to determine when to remove data. When the CPB 120supports operation on a sub-picture level, individual decoding units maybe removed rather than entire access units at one time. The decoder 112may include a Decoded Picture Buffer (DPB) 122. Each decoded picture isplaced in the DPB 122 for being referenced by the decoding process aswell as for output and cropping. A decoded picture is removed from theDPB at the later of the DPB output time or the time that it becomes nolonger needed for inter-prediction reference.

The decoder 112 may receive a message (e.g., picture timing SEI messageor other message). The decoder 112 may also determine whether thereceived message includes a common decoding unit CPB removal delayparameter (e.g., common du cpb removal delay). This may includeidentifying a flag (e.g., common du cpb removal delay flag) that is setwhen the common parameter is present in the picture timing SEI message.If the common parameter is present, the decoder 112 may determine thecommon decoding unit CPB removal delay parameter applicable to alldecoding units in the access unit. If the common parameter is notpresent, the decoder 112 may determine a separate decoding unit CPBremoval delay parameter for each decoding unit in the access unit. Thedecoder 112 may also remove decoding units from the CPB 120 using eitherthe common decoding unit CPB removal delay parameter or the separatedecoding unit CPB removal delay parameters.

The HRD described above may be one example of the decoder 112illustrated in FIG. 1A. Thus, an electronic device 102 may operate inaccordance with the HRD and CPB 120 and DPB 122 described above, in someconfigurations.

It should be noted that one or more of the elements or parts thereofincluded in the electronic device(s) 102 may be implemented in hardware.For example, one or more of these elements or parts thereof may beimplemented as a chip, circuitry or hardware components, etc. It shouldalso be noted that one or more of the functions or methods describedherein may be implemented in and/or performed using hardware. Forexample, one or more of the methods described herein may be implementedin and/or realized using a chipset, an Application-Specific IntegratedCircuit (ASIC), a Large-Scale Integrated circuit (LSI) or integratedcircuit, etc.

FIG. 1B is a block diagram illustrating another example of an encoder1908 and a decoder 1972. In this example, electronic device A 1902 andelectronic device B 1970 are illustrated. However, it should be notedthat the features and functionality described in relation to electronicdevice A 1902 and electronic device B 1970 may be combined into a singleelectronic device in some configurations.

Electronic device A 1902 includes the encoder 1908. The encoder 1908 mayinclude a base layer encoder 1910 and an enhancement layer encoder 1920.The video encoder 1908 is suitable for scalable video coding andmulti-view video coding, as described later. The encoder 1908 may beimplemented in hardware, software or a combination of both. In oneconfiguration, the encoder 1908 may be a high-efficiency video coding(HEVC) coder, including scalable and/or multi-view. Other coders maylikewise be used. Electronic device A 1902 may obtain a source 1906. Insome configurations, the source 1906 may be captured on electronicdevice A 1902 using an image sensor, retrieved from memory or receivedfrom another electronic device.

The encoder 1908 may code the source 1906 to produce a base layerbitstream 1934 and an enhancement layer bitstream 1936. For example, theencoder 1908 may code a series of pictures (e.g., video) in the source1906. In particular, for scalable video encoding for SNR scalabilityalso known as quality scalability the same source 1906 may be providedto the base layer and the enhancement layer encoder. In particular, forscalable video encoding for spatial scalability a downsampled source maybe used for the base layer encoder. In particular, for multi-viewencoding a different view source may be used for the base layer encoderand the enhancement layer encoder. The encoder 1908 may be similar tothe encoder 1782 described later in connection with FIG. 2B.

The bitstreams 1934, 1936 may include coded picture data based on thesource 1906. In some configurations, the bitstreams 1934, 1936 may alsoinclude overhead data, such as slice header information, PPSinformation, etc. As additional pictures in the source 1906 are coded,the bitstreams 1934, 1936 may include one or more coded pictures.

The bitstreams 1934, 1936 may be provided to the decoder 1972. Thedecoder 1972 may include a base layer decoder 1980 and an enhancementlayer decoder 1990. The video decoder 1972 is suitable for scalablevideo decoding and multi-view video decoding. In one example, thebitstreams 1934, 1936 may be transmitted to electronic device B 1970using a wired or wireless link In some cases, this may be done over anetwork, such as the Internet or a Local Area Network (LAN). Asillustrated in FIG. 1B, the decoder 1972 may be implemented onelectronic device B 1970 separately from the encoder 1908 on electronicdevice A 1902. However, it should be noted that the encoder 1908 anddecoder 1972 may be implemented on the same electronic device in someconfigurations. In an implementation where the encoder 1908 and decoder1972 are implemented on the same electronic device, for instance, thebitstreams 1934, 1936 may be provided over a bus to the decoder 1972 orstored in memory for retrieval by the decoder 1972. The decoder 1972 mayprovide a decoded base layer 1992 and decoded enhancement layerpicture(s) 1994 as output.

The decoder 1972 may be implemented in hardware, software or acombination of both. In one configuration, the decoder 1972 may be ahigh-efficiency video coding (HEVC) decoder, including scalable and/ormulti-view. Other decoders may likewise be used. The decoder 1972 may besimilar to the decoder 1812 described later in connection with FIG. 3B.Also, the base layer encoder and/or the enhancement layer encoder mayeach include a message generation module, such as that described inrelation to FIG. 1A. Also, the base layer decoder and/or the enhancementlayer decoder may include a coded picture buffer and/or a decodedpicture buffer, such as that described in relation to FIG. 1A. Inaddition, the electronic devices of FIG. 1B may operate in accordancewith the functions of the electronic devices of FIG. 1A, as applicable.

FIG. 2A is a block diagram illustrating one configuration of an encoder604 on an electronic device 602. It should be noted that one or more ofthe elements illustrated as included within the electronic device 602may be implemented in hardware, software or a combination of both. Forexample, the electronic device 602 includes an encoder 604, which may beimplemented in hardware, software or a combination of both. Forinstance, the encoder 604 may be implemented as a circuit, integratedcircuit, application-specific integrated circuit (ASIC), processor inelectronic communication with memory with executable instructions,firmware, field-programmable gate array (FPGA), etc., or a combinationthereof. In some configurations, the encoder 604 may be a HEVC coder.

The electronic device 602 may include a source 622. The source 622 mayprovide picture or image data (e.g., video) as one or more inputpictures 606 to the encoder 604. Examples of the source 622 may includeimage sensors, memory, communication interfaces, network interfaces,wireless receivers, ports, etc.

One or more input pictures 606 may be provided to an intra-frameprediction module and reconstruction buffer 624. An input picture 606may also be provided to a motion estimation and motion compensationmodule 646 and to a subtraction module 628.

The intra-frame prediction module and reconstruction buffer 624 maygenerate intra mode information 640 and an intra-signal 626 based on oneor more input pictures 606 and reconstructed data 660. The motionestimation and motion compensation module 646 may generate inter modeinformation 648 and an inter signal 644 based on one or more inputpictures 606 and a reference picture 678 from decoded picture buffer676. In some configurations, the decoded picture buffer 676 may includedata from one or more reference pictures in the decoded picture buffer676.

The encoder 604 may select between the intra signal 626 and the intersignal 644 in accordance with a mode. The intra signal 626 may be usedin order to exploit spatial characteristics within a picture in anintra-coding mode. The inter signal 644 may be used in order to exploittemporal characteristics between pictures in an inter coding mode. Whilein the intra coding mode, the intra signal 626 may be provided to thesubtraction module 628 and the intra mode information 640 may beprovided to an entropy coding module 642. While in the inter codingmode, the inter signal 644 may be provided to the subtraction module 628and the inter mode information 648 may be provided to the entropy codingmodule 642.

Either the intra signal 626 or the inter signal 644 (depending on themode) is subtracted from an input picture 606 at the subtraction module628 in order to produce a prediction residual 630. The predictionresidual 630 is provided to a transformation module 632. Thetransformation module 632 may compress the prediction residual 630 toproduce a transformed signal 634 that is provided to a quantizationmodule 636. The quantization module 636 quantizes the transformed signal634 to produce transformed and quantized coefficients (TQCs) 638.

The TQCs 638 are provided to an entropy coding module 642 and an inversequantization module 650. The inverse quantization module 650 performsinverse quantization on the TQCs 638 to produce an inverse quantizedsignal 652 that is provided to an inverse transformation module 654. Theinverse transformation module 654 decompresses the inverse quantizedsignal 652 to produce a decompressed signal 656 that is provided to areconstruction module 658.

The reconstruction module 658 may produce reconstructed data 660 basedon the decompressed signal 656. For example, the reconstruction module658 may reconstruct (modified) pictures. The reconstructed data 660 maybe provided to a deblocking filter 662 and to the intra predictionmodule and reconstruction buffer 624. The deblocking filter 662 mayproduce a filtered signal 664 based on the reconstructed data 660.

The filtered signal 664 may be provided to a sample adaptive offset(SAO) module 666. The SAO module 666 may produce SAO information 668that is provided to the entropy coding module 642 and an SAO signal 670that is provided to an adaptive loop filter (ALF) 672. The ALF 672produces an ALF signal 674 that is provided to the decoded picturebuffer 676. The ALF signal 674 may include data from one or morepictures that may be used as reference pictures.

The entropy coding module 642 may code the TQCs 638 to produce bitstreamA 614 a (e.g., encoded picture data). For example, the entropy codingmodule 642 may code the TQCs 638 using Context-Adaptive Variable LengthCoding (CAVLC) or Context-Adaptive Binary Arithmetic Coding (CABAC). Inparticular, the entropy coding module 642 may code the TQCs 638 based onone or more of intra mode information 640, inter mode information 648and SAO information 668. Bitstream A 614 a (e.g., encoded picture data)may be provided to a message generation module 608. The messagegeneration module 608 may be configured similarly to the messagegeneration module 108 described in connection with FIG. 1

For example, the message generation module 608 may generate a message(e.g., picture timing SEI message or other message) includingsub-picture parameters. The sub-picture parameters may include one ormore removal delays for decoding units (e.g., common du cpb removaldelay or du cpb removal delay[i]) and one or more NAL parameters (e.g.,common num nalus in du minus1 or num nalus in du minusl[i]). In someconfigurations, the message may be inserted into bitstream A 614 a toproduce bitstream B 614 b. Thus, the message may be generated after theentire bitstream A 614 a is generated (e.g., after most of bitstream B614 b is generated), for example. In other configurations, the messagemay not be inserted into bitstream A 614 a (in which case bitstream B614 b may be the same as bitstream A 614 a), but may be provided in aseparate transmission 610.

In some configurations, the electronic device 602 sends the bitstream614 to another electronic device. For example, the bitstream 614 may beprovided to a communication interface, network interface, wirelesstransmitter, port, etc. For instance, the bitstream 614 may betransmitted to another electronic device via LAN, the Internet, acellular phone base station, etc. The bitstream 614 may additionally oralternatively be stored in memory or other component on the electronicdevice 602.

FIG. 2B is a block diagram illustrating one configuration of a videoencoder 1782 on an electronic device 1702. The video encoder 1782 mayinclude an enhancement layer encoder 1706, a base layer encoder 1709, aresolution upscaling block 1770 and an output interface 1780. The videoencoder of FIG. 2B, for example, is suitable for scalable video codingand multi-view video coding, as described herein.

The enhancement layer encoder 1706 may include a video input 1781 thatreceives an input picture 1704. The output of the video input 1781 maybe provided to an adder/subtractor 1783 that receives an output of aprediction selection 1750. The output of the adder/subtractor 1783 maybe provided to a transform and quantize block 1752. The output of thetransform and quantize block 1752 may be provided to an entropy encoding1748 block and a scaling and inverse transform block 1772. After entropyencoding 1748 is performed, the output of the entropy encoding block1748 may be provided to the output interface 1780. The output interface1780 may output both the encoded base layer video bitstream 1707 and theencoded enhancement layer video bitstream 1710.

The output of the scaling and inverse transform block 1772 may beprovided to an adder 1779. The adder 1779 may also receive the output ofthe prediction selection 1750. The output of the adder 1779 may beprovided to a deblocking block 1751. The output of the deblocking block1751 may be provided to a reference buffer 1794. An output of thereference buffer 1794 may be provided to a motion compensation block1754. The output of the motion compensation block 1754 may be providedto the prediction selection 1750. An output of the reference buffer 1794may also be provided to an intra predictor 1756. The output of the intrapredictor 1756 may be provided to the prediction selection 1750. Theprediction selection 1750 may also receive an output of the resolutionupscaling block 1770.

The base layer encoder 1709 may include a video input 1762 that receivesa downsampled input picture, or other image content suitable for combingwith another image, or an alternative view input picture or the sameinput picture 1703 (i.e., the same as the input picture 1704 received bythe enhancement layer encoder 1706). The output of the video input 1762may be provided to an encoding prediction loop 1764. Entropy encoding1766 may be provided on the output of the encoding prediction loop 1764.The output of the encoding prediction loop 1764 may also be provided toa reference buffer 1768. The reference buffer 1768 may provide feedbackto the encoding prediction loop 1764. The output of the reference buffer1768 may also be provided to the resolution upscaling block 1770. Onceentropy encoding 1766 has been performed, the output may be provided tothe output interface 1780. The encoded base layer video bitstream 1707and/or the encoded enhancement layer video bitstream 1710 may beprovided to one or more message generation modules, as desired.

FIG. 3A is a block diagram illustrating one configuration of a decoder712 on an electronic device 702. The decoder 712 may be included in anelectronic device 702. For example, the decoder 712 may be a HEVCdecoder. The decoder 712 and one or more of the elements illustrated asincluded in the decoder 712 may be implemented in hardware, software ora combination of both. The decoder 712 may receive a bitstream 714(e.g., one or more encoded pictures and overhead data included in thebitstream 714) for decoding. In some configurations, the receivedbitstream 714 may include received overhead data, such as a message(e.g., picture timing SEI message or other message), slice header, PPS,etc. In some configurations, the decoder 712 may additionally receive aseparate transmission 710. The separate transmission 710 may include amessage (e.g., a picture timing SEI message or other message). Forexample, a picture timing SEI message or other message may be receivedin a separate transmission 710 instead of in the bitstream 714. However,it should be noted that the separate transmission 710 may be optionaland may not be utilized in some configurations.

The decoder 712 includes a CPB 720. The CPB 720 may be configuredsimilarly to the CPB 120 described in connection with FIG. 1 above. Thedecoder 712 may receive a message (e.g., picture timing SEI message orother message) with sub-picture parameters and remove and decodedecoding units in an access unit based on the sub-picture parameters. Itshould be noted that one or more access units may be included in thebitstream and may include one or more of encoded picture data andoverhead data.

The Coded Picture Buffer (CPB) 720 may provide encoded picture data toan entropy decoding module 701. The encoded picture data may be entropydecoded by an entropy decoding module 701, thereby producing a motioninformation signal 703 and quantized, scaled and/or transformedcoefficients 705.

The motion information signal 703 may be combined with a portion of areference frame signal 798 from a decoded picture buffer 709 at a motioncompensation module 780, which may produce an inter-frame predictionsignal 782. The quantized, descaled and/or transformed coefficients 705may be inverse quantized, scaled and inverse transformed by an inversemodule 707, thereby producing a decoded residual signal 784. The decodedresidual signal 784 may be added to a prediction signal 792 to produce acombined signal 786. The prediction signal 792 may be a signal selectedfrom either the inter-frame prediction signal 782 produced by the motioncompensation module 780 or an intra-frame prediction signal 790 producedby an intra-frame prediction module 788. In some configurations, thissignal selection may be based on (e.g., controlled by) the bitstream714.

The intra-frame prediction signal 790 may be predicted from previouslydecoded information from the combined signal 786 (in the current frame,for example). The combined signal 786 may also be filtered by ade-blocking filter 794. The resulting filtered signal 796 may be writtento decoded picture buffer 709. The resulting filtered signal 796 mayinclude a decoded picture. The decoded picture buffer 709 may provide adecoded picture which may be outputted 718. In some cases 709 may be aconsidered as frame memory.

FIG. 3B is a block diagram illustrating one configuration of a videodecoder 1812 on an electronic device 1802. The video decoder 1812 mayinclude an enhancement layer decoder 1815 and a base layer decoder 1813.The video decoder 812 may also include an interface 1889 and resolutionupscaling 1870. The video decoder of FIG. 3B, for example, is suitablefor scalable video coding and multi-view video encoded, as describedherein.

The interface 1889 may receive an encoded video stream 1885. The encodedvideo stream 1885 may consist of base layer encoded video stream andenhancement layer encoded video stream. These two streams may be sentseparately or together. The interface 1889 may provide some or all ofthe encoded video stream 1885 to an entropy decoding block 1886 in thebase layer decoder 1813. The output of the entropy decoding block 1886may be provided to a decoding prediction loop 1887. The output of thedecoding prediction loop 1887 may be provided to a reference buffer1888. The reference buffer may provide feedback to the decodingprediction loop 1887. The reference buffer 1888 may also output thedecoded base layer video stream 1884.

The interface 1889 may also provide some or all of the encoded videostream 1885 to an entropy decoding block 1890 in the enhancement layerdecoder 1815. The output of the entropy decoding block 1890 may beprovided to an inverse quantization block 1891. The output of theinverse quantization block 1891 may be provided to an adder 1892. Theadder 1892 may add the output of the inverse quantization block 1891 andthe output of a prediction selection block 1895. The output of the adder1892 may be provided to a deblocking block 1893. The output of thedeblocking block 1893 may be provided to a reference buffer 1894. Thereference buffer 1894 may output the decoded enhancement layer videostream 1882. The output of the reference buffer 1894 may also beprovided to an intra predictor 1897. The enhancement layer decoder 1815may include motion compensation 1896. The motion compensation 1896 maybe performed after the resolution upscaling 1870. The predictionselection block 1895 may receive the output of the intra predictor 1897and the output of the motion compensation 1896. Also, the decoder mayinclude one or more coded picture buffers, as desired, such as togetherwith the interface 1889.

FIG. 4 illustrates various components that may be utilized in atransmitting electronic device 802. One or more of the electronicdevices 102, 602, 702 described herein may be implemented in accordancewith the transmitting electronic device 802 illustrated in FIG. 4.

The transmitting electronic device 802 includes a processor 817 thatcontrols operation of the electronic device 802. The processor 817 mayalso be referred to as a CPU. Memory 811, which may include bothread-only memory (ROM), random access memory (RAM) or any type of devicethat may store information, provides instructions 813 a (e.g.,executable instructions) and data 815 a to the processor 817. A portionof the memory 811 may also include non-volatile random access memory(NVRAM). The memory 811 may be in electronic communication with theprocessor 817.

Instructions 813 b and data 815 b may also reside in the processor 817.Instructions 813 b and/or data 815 b loaded into the processor 817 mayalso include instructions 813 a and/or data 815 a from memory 811 thatwere loaded for execution or processing by the processor 817. Theinstructions 813 b may be executed by the processor 817 to implement thesystems and methods disclosed herein. For example, the instructions 813b may be executable to perform one or more of the methods 200, 300, 400,500 described above.

The transmitting electronic device 802 may include one or morecommunication interfaces 819 for communicating with other electronicdevices (e.g., receiving electronic device). The communicationinterfaces 819 may be based on wired communication technology, wirelesscommunication technology, or both. Examples of a communication interface819 include a serial port, a parallel port, a Universal Serial Bus(USB), an Ethernet adapter, an IEEE 1394 bus interface, a small computersystem interface (SCSI) bus interface, an infrared (IR) communicationport, a Bluetooth wireless communication adapter, a wireless transceiverin accordance with 3^(rd) Generation Partnership Project (3GPP)specifications and so forth.

The transmitting electronic device 802 may include one or more outputdevices 823 and one or more input devices 821. Examples of outputdevices 823 include a speaker, printer, etc. One type of output devicethat may be included in an electronic device 802 is a display device825. Display devices 825 used with configurations disclosed herein mayutilize any suitable image projection technology, such as a cathode raytube (CRT), liquid crystal display (LCD), light-emitting diode (LED),gas plasma, electroluminescence or the like. A display controller 827may be provided for converting data stored in the memory 811 into text,graphics, and/or moving images (as appropriate) shown on the display825. Examples of input devices 821 include a keyboard, mouse,microphone, remote control device, button, joystick, trackball,touchpad, touchscreen, lightpen, etc.

The various components of the transmitting electronic device 802 arecoupled together by a bus system 829, which may include a power bus, acontrol signal bus and a status signal bus, in addition to a data bus.However, for the sake of clarity, the various buses are illustrated inFIG. 4 as the bus system 829. The transmitting electronic device 802illustrated in FIG. 4 is a functional block diagram rather than alisting of specific components.

FIG. 5 is a block diagram illustrating various components that may beutilized in a receiving electronic device 902. One or more of theelectronic devices 102, 602, 702 described herein may be implemented inaccordance with the receiving electronic device 902 illustrated in FIG.5.

The receiving electronic device 902 includes a processor 917 thatcontrols operation of the electronic device 902. The processor 917 mayalso be referred to as a CPU. Memory 911, which may include bothread-only memory (ROM), random access memory (RAM) or any type of devicethat may store information, provides instructions 913 a (e.g.,executable instructions) and data 915 a to the processor 917. A portionof the memory 911 may also include non-volatile random access memory(NVRAM). The memory 911 may be in electronic communication with theprocessor 917.

Instructions 913 b and data 915 b may also reside in the processor 917.Instructions 913 b and/or data 915 b loaded into the processor 917 mayalso include instructions 913 a and/or data 915 a from memory 911 thatwere loaded for execution or processing by the processor 917. Theinstructions 913 b may be executed by the processor 917 to implement thesystems and methods disclosed herein. For example, the instructions 913b may be executable to perform one or more of the methods 200, 300, 400,500 described above.

The receiving electronic device 902 may include one or morecommunication interfaces 919 for communicating with other electronicdevices (e.g., a transmitting electronic device). The communicationinterface 919 may be based on wired communication technology, wirelesscommunication technology, or both. Examples of a communication interface919 include a serial port, a parallel port, a Universal Serial Bus(USB), an Ethernet adapter, an IEEE 1394 bus interface, a small computersystem interface (SCSI) bus interface, an infrared (IR) communicationport, a Bluetooth wireless communication adapter, a wireless transceiverin accordance with 3^(rd) Generation Partnership Project (3GPP)specifications and so forth.

The receiving electronic device 902 may include one or more outputdevices 923 and one or more input devices 921. Examples of outputdevices 923 include a speaker, printer, etc. One type of output devicethat may be included in an electronic device 902 is a display device925. Display devices 925 used with configurations disclosed herein mayutilize any suitable image projection technology, such as a cathode raytube (CRT), liquid crystal display (LCD), light-emitting diode (LED),gas plasma, electroluminescence or the like. A display controller 927may be provided for converting data stored in the memory 911 into text,graphics, and/or moving images (as appropriate) shown on the display925. Examples of input devices 921 include a keyboard, mouse,microphone, remote control device, button, joystick, trackball,touchpad, touchscreen, lightpen, etc.

The various components of the receiving electronic device 902 arecoupled together by a bus system 929, which may include a power bus, acontrol signal bus and a status signal bus, in addition to a data bus.However, for the sake of clarity, the various buses are illustrated inFIG. 5 as the bus system 929. The receiving electronic device 902illustrated in FIG. 5 is a functional block diagram rather than alisting of specific components.

FIG. 6 is a block diagram illustrating one configuration of anelectronic device 1002 in which systems and methods for sending amessage may be implemented. The electronic device 1002 includes encodingmeans 1031 and transmitting means 1033. The encoding means 1031 andtransmitting means 1033 may generate a bitstream 1014. FIG. 4 aboveillustrates one example of a concrete apparatus structure of FIG. 6. ADSP may be realized by software.

FIG. 7 is a block diagram illustrating one configuration of anelectronic device 1102 in which systems and methods for buffering abitstream 1114 may be implemented. The electronic device 1102 mayinclude receiving means 1135 and decoding means 1137. The receivingmeans 1135 and decoding means 1137 may receive a bitstream 1114. FIG. 5above illustrates one example of a concrete apparatus structure of FIG.7. A DSP may be realized by software.

The decoding process for reference picture set (RPS) may be invoked.Reference picture set is a set of reference pictures associated with apicture, consisting of all reference pictures that are prior to theassociated picture in decoding order, that may be used for interprediction of the associated picture or any picture following theassociated picture in decoding order.

The bitstream of the video may include a syntax structure that is placedinto logical data packets generally referred to as Network AbstractionLayer (NAL) units. Each NAL unit includes a NAL unit header, such as atwo-byte NAL unit header (e.g., 16 bits), to identify the purpose of theassociated data payload. For example, each coded slice (and/or picture)may be coded in one or more slice (and/or picture) NAL units. Other NALunits may be included for other categories of data, such as for example,supplemental enhancement information, coded slice of temporal sub-layeraccess (TSA) picture, coded slice of step-wise temporal sub-layer access(STSA) picture, coded slice a non-TSA, non-STSA trailing picture, codedslice of broken link access picture, coded slice of instantaneousdecoded refresh picture, coded slice of clean random access picture,coded slice of decodable leading picture, coded slice of tagged fordiscard picture, video parameter set, sequence parameter set, pictureparameter set, access unit delimiter, end of sequence, end of bitstream,filler data, and/or sequence enhancement information message. Table (1)illustrates one example of NAL unit codes and NAL unit type classes.Other NAL unit types may be included, as desired. It should also beunderstood that the NAL unit type values for the NAL units shown in theTable (1) may be reshuffled and reassigned. Also additional NAL unittypes may be added. Also some NAL unit types may be removed.

An intra random access point (IRAP) picture is a coded picture for whicheach video coding layer NAL unit has nal_unit_type in the range ofBLA_W_LP to RSV_IRAP_VCL23, inclusive as shown in Table (1). An IRAPpicture contains only Intra coded (I) slices. An instantaneous decodingrefresh (IDR) picture is an IRAP picture for which each video codinglayer NAL unit has nal_unit_type equal to IDR_W_RADL or IDR_N_LP asshown in Table (1. An instantaneous decoding referesh (IDR) picturecontains only I slices, and may be the first picture in the bitstream indecoding order, or may appear later in the bitstream. Each IDR pictureis the first picture of a coded video sequence (CVS) in decoding order.A broken link access (BLA) picture is an IRAP picture for which eachvideo coding layer NAL unit has nal_uni_type equal to BLA_W_LP,BLA_W_RADL, or BLA_N_LP as shown in Table (1). A BLA picture containsonly I slices, and may be the first picture in the bitstream in decodingorder, or may appear later in the bitstream. Each BLA picture begins anew coded video sequence, and has the same effect on the decodingprocess as an IDR picture. However, a BLA picture contains syntaxelements that specify a non-empty reference picture set. Clean randomaccess (CRA) access unit is an access unit in which the coded picture isa CRA picture. Clean random access (CRA) picture is an IRAP picture forwhich each VCL NAL unit has nal_unit_type equal to CRA_NUT as shown inTable (1). A CRA picture contains only I slices, and may be the firstpicture in the bitstream in decoding order, or may appear later in thebitstream. A CRA picture may have associated RADL or RASL pictures. Whena CRA picture has NoRaslOutputFlag equal to 1, the associated RASLpictures are not output by the decoder, because they may not bedecodable, as they may contain references to pictures that are notpresent in the bitstream.

TABLE (1) NAL Content of NAL unit and unit Name of raw byte sequencepayload type nal_unit_type nal_unit_type (RBSP) syntax structure class 0 TRAIL_N Coded slice segment of a Video  1 TRAIL_R non-TSA, non-STSAtrailing Coding picture Layer slice_segment_layer_rbsp( ) (VCL)  2 TSA_NCoded slice segment of a VCL  3 TSA_R temporal sub-layer access (TSA)picture slice_segment_layer_rbsp( )  4 STSA_N Coded slice segment of anVCL  5 STSA_R Step-wise Temporal sub- layer access (STSA) pictureslice_segment_layer_rbsp( )  6 RADL_N Coded slice segment of a VCL  7RADL_R random access decodable leading (RADL) pictureslice_segment_layer_rbsp( )  8 RASL_N Coded slice segment of a VCL  9RASL_R random access skipped leading (RASL) pictureslice_segment_layer_rbsp( ) 10 RSV_VCL_N10 Reserved non-IRAP sub- VCL 12RSV_VCL_N12 layer non-reference VCL NAL 14 RSV_VCL_N14 unit types 11RSV_VCL_R11 Reserved non-IRAP sub- VCL 13 RSV_VCL_R13 layer referenceVCL NAL unit 15 RSV_VCL_R15 types 16 BLA_W_LP Coded slice segment of aVCL 17 BLA_W_RADL broken link access (BLA) 18 BLA_N_LP pictureslice_segment_layer_rbsp( ) 19 IDR_W_RADL Coded slice segment of an VCL20 IDR_N_LP instantaneous decoding refresh (IDR) pictureslice_segment_layer_rbsp( ) 21 CRA_NUT Coded slice segment of a VCLclean random access (CRA) picture slice_segment_layer_rbsp( ) 22RSV_IRAP_VCL22 Reserved IRAP VCL NAL VCL 23 RSV_IRAP_VCL23 unit types 24. . . 31 RSV_VCL24 . . . RSV_VCL31 Reserved non-IRAP VCL VCL NAL unittypes 32 VPS_NUT Video parameter set non- video_parameter_set_rbsp( )video coding layer (non- VCL) 33 SPS_NUT Sequence parameter set non-seq_parameter_set_rbsp( ) VCL 34 PPS_NUT Picture parameter set non-pic_parameter_set_rbsp( ) VCL 35 AUD_NUT Access unit delimiter non-access_unit_delimiter_rbsp( ) VCL 36 EOS_NUT End of sequence non-end_of_seq_rbsp( ) VCL 37 EOB_NUT End of bitstream non-end_of_bitstream_rbsp( ) VCL 38 FD_NUT Filler data non-filler_data_rbsp( ) VCL 39 PREFIX_SEI_NUT Supplemental enhancement non-40 SUFFIX_SEI_NUT information VCL sei_rbsp( ) 41 . . . 47 RSV_NVCL41 . .. RSV_NVCL47 Reserved non- VCL 48 . . . 63 UNSPEC48 . . . UNSPEC63Unspecified non- VCL

Referring to Table (2), the NAL unit header syntax may include two bytesof data, namely, 16 bits. The first bit is a “forbidden_zero_bit” whichis always set to zero at the start of a NAL unit. The next six bits is a“nal_unit_type” which specifies the type of raw byte sequence payloads(“RBSP”) data structure contained in the NAL unit as shown in Table (1).The next 6 bits is a “nuh_layer_id” which specify the indentifier of thelayer. In some cases these six bits may be specified as“nuh_reserved_zero_6bits” instead. The nuh_reserved_zero_6bits may beequal to 0 in the base specification of the standard. In a scalablevideo coding and/or syntax extensions nuh_layer_id may specify that thisparticular NAL unit belongs to the layer identified by the value ofthese 6 bits. The next syntax element is “nuh_temporal_id_plus1”. Thenuh_temporal_id_plus1 minus 1 may specify a temporal identifier for theNAL unit. The variable temporal identifier TemporalId may be specifiedas TemporakId=nuh_temporal_id_plus1−1. The temporal identifierTemporalId is used to identify a temporal sub-layer. The variableHighestTid identifies the highest temporal sub-layer to be decoded.

TABLE (2) nal_unit_header( ) { Descriptor  forbidden_zero_bit f(1) nal_unit_type u(6)  nuh_layer_id u(6)  nuh_temporal_id_plus1 u(3) }

Referring to FIG. 8A, as previously described the NAL unit header syntaxmay include two bytes of data, namely, 16 bits. The first bit is a“forbidden_zero_bit” which is always set to zero at the start of a NALunit. The next six bits is a “nal_unit type” which specifies the type ofraw byte sequence payloads (“RBSP”) data structure contained in the NALunit. The next 6 bits is a “nuh_reserved_zero 6bits”. Thenuh_reserved_zero_6bits may be equal to 0 in the base specification ofthe standard. Other values of nuh_reserved_zero_6bits may be specifiedas desired. Decoders may ignore (i.e., remove from the bitstream anddiscard) all NAL units with values of nuh_reserved_zero_6bits not equalto 0 when handling a stream based on the base specification of thestandard. In a scalable or other extension nuh_reserved_zero_6bits mayspecify other values, to signal scalable video coding and/or syntaxextensions. In some cases syntax element nuh_reserved_zero_6bits may becalled reserved_zero₆bits. In some cases the syntax elementnuh_reserved_zero_6bits may be called as layer_id_plus1 or layer_id, asillustrated in FIG. 8B and FIG. 8C. In this case the element layer_idwill be layer_id_plus1 minus 1. In this case it may be used to signalinformation related to layer of scalable coded video. The next syntaxelement is “nuh_temporal_id_plus1”. nuh_temporal_id_plus1 minus 1 mayspecify a temporal identifier for the NAL unit. The variable temporalidentifier TemporalId may be specified asTemporalId=nuh_temporal_id_plus1−1.

Referring to FIG. 9, a general NAL unit syntax structure is illustrated.The NAL unit header two byte syntax of FIG. 8 is included in thereference to nal_unit_header( ) of FIG. 9. The remainder of the NAL unitsyntax primarily relates to the RBSP.

One existing technique for using the “nuh_reserved_zero_6bits” is tosignal scalable video coding information by partitioning the 6 bits ofthe nuh_reserved_zero_6bits into distinct bit fields, namely, one ormore of a dependency ID, a quality ID, a view ID, and a depth flag, eachof which refers to the identification of a different layer of thescalable coded video. Accordingly, the 6 bits indicate what layer of thescalable encoding technique this particular NAL unit belongs to. Then ina data payload, such as a video parameter set (“VPS”) extension syntax(“scalability_type”) as illustrated in FIG. 10, the information aboutthe layer is defined. The VPS extension syntax of FIG. 10 includes 4bits for scalability type (syntax element scalability_type) whichspecifies the scalability types in use in the coded video sequence andthe dimensions signaled through layer_id_plus1 (or layer_id) in the NALunit header. When the scalability type is equal to 0, the coded videosequence conforms to the base specification, thus layer id plusl of allNAL units is equal to 0 and there are no NAL units belonging to anenhancement layer or view. Higher values of the scalability type areinterpreted as illustrated in FIG. 11.

The layer_id_dim_len[i] specifies the length, in bits, of the i-thscalability dimension ID. The sum of the values layer_id_dim_len[i] forall i values in the range of 0 to 7 is less than or equal to 6. Thevps_extension_byte_alignment_reserved_zero_bit is zero. Thevps_layer_id[i] specifies the value of layer_id of the i-th layer towhich the following layer dependency information applies. Thenum_direct_ref_layers[i] specifies the number of layers the i-th layerdirectly depends on. The ref_layer_id[i] [j] identifies the j-th layerthe i-th layer directly depends on.

In this manner, the existing technique signals the scalabilityidentifiers in the NAL unit and in the video parameter set to allocatethe bits among the scalability types listed in FIG. 11. Then for eachscalability type, FIG. 11 defines how many dimensions are supported. Forexample, scalability type 1 has 2 dimensions (i.e., spatial andquality). For each of the dimensions, the layer_id_dim_len[i] definesthe number of bits allocated to each of these two dimensions, where thetotal sum of all the values of layer_id_dim_len[i] is less than or equalto 6, which is the number of bits in the nuh_reserved_zero 6bits of theNAL unit header. Thus, in combination the technique identifies whichtypes of scalability is in use and how the 6 bits of the NAL unit headerare allocated among the scalability.

As previously described, scalable video coding is a technique ofencoding a video bitstream that also contains one or more subsetbitstreams. A subset video bitstream may be derived by dropping packetsfrom the larger video to reduce the bandwidth required for the subsetbitstream. The subset bitstream may represent a lower spatial resolution(smaller screen), lower temporal resolution (lower frame rate), or lowerquality video signal. For example, a video bitstream may include 5subset bitstreams, where each of the subset bitstreams adds additionalcontent to a base bitstream. Hannuksela, et al., “Test Model forScalable Extensions of High Efficiency Video Coding (HEVC)” JCTVC-L0453,Shanghai, October 2012, is hereby incorporated by reference herein inits entirety. Chen, et al., “SHVC Draft Text 1,” JCTVC-L1008, Geneva,March, 2013, is hereby incorporated by reference herein in its entirety.J. Chen, J. Boyce, Y. Ye, M Hannuksela, SHVC Draft 3, JCTVC-N1008,Vienna, August 2013; and Y. Chen, Y.-K. Wang, A. K. Ramasubromanian,MV-HEVC/SHVC HLS: Cross-layer POC Alignment, JCTVC-N0244, Vienna, July2013; each of which is incorporated by reference herein in its entirety.

As previously described, multi-view video coding is a technique ofencoding a video bitstream that also contains one or more otherbitstreams representative of alternative views. For example, themultiple views may be a pair of views for stereoscopic video. Forexample, the multiple views may represent multiple views of the samescene from different viewpoints. The multiple views generally contain alarge amount of interview statistical dependencies, since the images areof the same scene from different viewpoints. Therefore, combinedtemporal and inter-view prediction may achieve efficient multi-viewencoding. For example, a frame may be efficiently predicted not onlyfrom temporally related frames, but also from the frames of neighboringviewpoints. Hannuksela, et al., “Common specification text for scalableand multi-view extensions,” JCTVC-L0452, Geneva, January 2013, is herebyincorporated by reference herein in its entirety. Tech, et. al. “MV-HEVCDraft Text 3 (ISO/IEC 23008-2:201x/PDAM2),” JCT3V-C1004 d3, Geneva,January 2013, is hereby incorporated by reference herein in itsentirety. G. Tech, K. Wegner, Y. Chen, M. Hannuksela, J. Boyce, “MV-HEVCDraft Text 5 (ISO/IEC 203008-2:201x/PDAM2), JCTVC-E1004, Vienna, August2013, is hereby incorporated by reference herein in its entirety. G.Tech, K. Wegner, Y. Chen, M. Hannuksela, J. Boyce, “MV-HEVC Draft Text7”, JCT3V-G1004, San Jose, January 2014, is hereby incorporated byreference herein in its entirety.

Chen, et al., “SHVC Draft Text 1,” JCTVC-L1008, Geneva, January 2013;Hannuksela, et al. “Test Model for Scalable Extensions of HighEfficiency Video Coding (HEVC),” JCTVC-L0453-spec-text, Shanghai,October 2012; and Hannuksela, “Draft Text for Multiview Extension ofHigh Efficiency Video Coding (HEVC),” JCTVC-L0452-spec-text-r1,Shanghai, October 2012; each of which is incorporated by referenceherein in its entirety, each have an output order decoded picture buffer(DPB) which operates based on usingsps_max_num_reorder_pics[HighestTid],sps_max_latency_increase_plus1[HighestTid] and sps_max_dec_picbuffering[HighestTid] syntax elements for the output and removal ofpictures 0 from the DPB. This information is signaled in the videoparameter set for the base layer, which provides buffering informationfor the video content including the enhancement layers, if any.

Referring to FIG. 12, when coding scalable high efficiency coding(“SVHC”) the base layer may include one or more SPS and may also includeone or more PPS. Also, each enhancement layer may include one or moreSPS and may also include one or more PPS. In FIG. 12 SPS+ indicates oneor more SPS and PPS+ indicates one or more PPS being signaled for aparticular base or enhancement layer. In this manner, for a videobitstream having both a base layer and one or more enhancement layers,the collective number of SPS and PPS data sets becomes significanttogether with the required bandwidth to transmit such data, which tendsto be limited in many applications. With such bandwidth limitations, itis desirable to limit the data that needs to be transmitted, and locatethe data in the bitstream in an effective manner. Each layer may haveone SPS and/or PPS that is activate at any particular time, and mayselect a different active SPS and/or PPS, as desired.

An input picture may comprise a plurality of coded tree blocks (e.g.,generally referred to herein as blocks) may be partitioned into one orseveral slices. The values of the samples in the area of the picturethat a slice represents may be properly decoded without the use of datafrom other slices provided that the reference pictures used at theencoder and the decoder are the same and that de-blocking filtering doesnot use information across slice boundaries. Therefore, entropy decodingand block reconstruction for a slice does not depend on other slices. Inparticular, the entropy coding state may be reset at the start of eachslice. The data in other slices may be marked as unavailable whendefining neighborhood availability for both entropy decoding andreconstruction. The slices may be entropy decoded and reconstructed inparallel. No intra prediction and motion-vector prediction is preferablyallowed across the boundary of a slice. In contrast, de-blockingfiltering may use information across slice boundaries.

FIG. 13 illustrates an exemplary video picture 2090 comprising elevenblocks in the horizontal direction and nine blocks in the verticaldirection (nine exemplary blocks labeled 2091-2099). FIG. 13 illustratesthree exemplary slices: a first slice denoted “SLICE #0” 2080, a secondslice denoted “SLICE #1” 2081 and a third slice denoted “SLICE #2” 2082.The decoder may decode and reconstruct the three slices 2080, 2081, 2082in parallel. Each of the slices may be transmitted in scan line order ina sequential manner. At the beginning of the decoding/reconstructionprocess for each slice, context models are initialized or reset andblocks in other slices are marked as unavailable for both entropydecoding and block reconstruction. The context model generallyrepresents the state of the entropy encoder and/or decoder. Thus, for ablock, for example, the block labeled 2093, in “SLICE #1,” blocks (forexample, blocks labeled 2091 and 2092) in “SLICE #0” may not be used forcontext model selection or reconstruction. Whereas, for a block, forexample, the block labeled 2095, in “SLICE #1,” other blocks (forexample, blocks labeled 2093 and 2094) in “SLICE #1” may be used forcontext model selection or reconstruction. Therefore, entropy decodingand block reconstruction proceeds serially within a slice. Unless slicesare defined using a flexible block ordering (FMO), blocks within a sliceare processed in the order of a raster scan.

Flexible block ordering defines a slice group to modify how a picture ispartitioned into slices. The blocks in a slice group are defined by ablock-to-slice-group map, which is signaled by the content of thepicture parameter set and additional information in the slice headers.The block-to-slice-group map consists of a slice-group identificationnumber for each block in the picture. The slice-group identificationnumber specifies to which slice group the associated block belongs. Eachslice group may be partitioned into one or more slices, wherein a sliceis a sequence of blocks within the same slice group that is processed inthe order of a raster scan within the set of blocks of a particularslice group. Entropy decoding and block reconstruction proceeds seriallywithin a slice group.

FIG. 14 depicts an exemplary block allocation into three slice groups: afirst slice group denoted “SLICE GROUP #0” 2083, a second slice groupdenoted “SLICE GROUP #1” 2084 and a third slice group denoted “SLICEGROUP #2” 2085. These slice groups 2083, 2084, 2085 may be associatedwith two foreground regions and a background region, respectively, inthe picture 2090.

The arrangement of slices, as illustrated in FIG. 14, may be limited todefining each slice between a pair of blocks in the image scan order,also known as raster scan or a raster scan order. This arrangement ofscan order slices is computationally efficient but does not tend to lenditself to the highly efficient parallel encoding and decoding. Moreover,this scan order definition of slices also does not tend to group smallerlocalized regions of the image together that are likely to have commoncharacteristics highly suitable for coding efficiency. The arrangementof slices 2083, 2084, 2085, as illustrated in FIG. 14, is highlyflexible in its arrangement but does not tend to lend itself to highefficient parallel encoding or decoding. Moreover, this highly flexibledefinition of slices is computationally complex to implement in adecoder.

Referring to FIG. 15, a tile technique divides an image into a set ofrectangular (inclusive of square) regions. The blocks (alternativelyreferred to as largest coding units or coded treeblocks in some systems)within each of the tiles are encoded and decoded in a raster scan order.The arrangement of tiles are likewise encoded and decoded in a rasterscan order. Accordingly, there may be any suitable number of columnboundaries (e.g., 0 or more) and there may be any suitable number of rowboundaries (e.g., 0 or more). Thus, the frame may define one or moreslices, such as the one slice illustrated in FIG. 15. In someembodiments, blocks located in different tiles are not available forintra-prediction, motion compensation, entropy coding context selectionor other processes that rely on neighboring block information.

Referring to FIG. 16, the tile technique is shown dividing an image intoa set of three rectangular columns. The blocks (alternatively referredto as largest coding units or coded treeblocks in some systems) withineach of the tiles are encoded and decoded in a raster scan order. Thetiles are likewise encoded and decoded in a raster scan order. One ormore slices may be defined in the scan order of the tiles. Each of theslices are independently decodable. For example, slice 1 may be definedas including blocks 1-9, slice 2 may be defined as including blocks10-28, and slice 3 may be defined as including blocks 29-126 which spansthree tiles. The use of tiles facilitates coding efficiency byprocessing data in more localized regions of a frame.

Referring to FIG. 17, the base layer and the enhancement layers may eachinclude tiles which each collectively form a picture or a portionthereof. The coded pictures from the base layer and one or moreenhancement layers may collectively form an access unit. The access unitmay be defined as a set of NAL units that are associated with each otheraccording to a specified classification rule, are consecutive indecoding order, and/or contain the VCL NAL units of all coded picturesassociated with the same output time (picture order count or otherwise)and their associated non-VCL NAL units. The VCL NAL is the video codinglayer of the network abstraction layer. Similarly, the coded picture maybe defined as a coded representation of a picture comprising VCL NALunits with a particular value of nuh layer id within an access unit andcontaining all coding tree units of the picture. Additional descriptionsare described in B. Bros, W-J. Han, J-R. Ohm, G. J. Sullivan, and T.Wiegand, “High efficiency video coding (HEVC) text specification draft10,” JCTVC-L1003, Geneva, January 2013; J. Chen, J. Boyce, Y. Ye, M. M.Hannuksela, “SHVC Draft Text 2,” JCTVC-M1008, Incheon, May 2013; G.Tech, K. Wegner, Y. Chen, M. Hannuksela, J. Boyce, “MV-HEVC Draft Text 4(ISO/IEC 23008-2:201x/PDAM2),” JCTVC-D1004, Incheon, May 2013; each ofwhich is incorporated by reference herein in its entirety. J. Chen, J.Boyce, Y. Ye, M. M. Hannuksela, “High Efficiency Video Coding (HEVC)Scalable Extension Draft 5”, JCTVC-P1008, San Jose, January 2014,incorporated by reference herein in its entirety. Y. K. Wang, J. Chen,Y. Chen, Hendry, A. K. Ramasubramonian, “Support of AVC base layer inSHVC”, JCTVC-P0184v4, February 2014, incorporated by reference herein inits entirety.

Referring to FIGS. 18A-18D, each slice may include a slice segmentheader. In some cases a slice segment header may be called slice header.Within the slice segment header there includes syntax elements that areused for inter-layer prediction. This inter-layer prediction defineswhat other layers the slice may depend upon. In other words thisinter-layer prediction defines what other layers the slice may use asits reference layers. The reference layers may be used for sampleprediction and/or for motion filed prediction. Referring to FIG. 19 byway of example, enhancement layer 3 may depend upon enhancement layer 2,and base layer layer 0. This dependency relationship may be expressed inthe form of a list, such as, [2, 0].

The NumDirectRefLayers for a layer may be derived based upon a directdependency flag[i] [j] that when equal to 0 specifies that the layerwith index j is not a direct reference layer for the layer with index i.The direct dependency flag[i] [j] equal to 1 specifies that the layerwith index j may be a direct reference layer for the layer with index i.When the direct dependency flag[i] [j] is not present for i and j in therange of 0 to vps_max_layers_minus1, it is inferred to be equal to 0.

The direct_dep_type_len_minus2 plus 2 specifies the number of bits ofthe direct dependency type[i] [j] syntax element. In bitstreamsconforming to this version of this Specification the value ofdirect_dep_type_len_minus2 shall be equal 0. Although the value ofdirect_dep_type_len_minus2 shall be equal to 0 in this version of thisSpecification, decoders shall allow other values ofdirect_dep_type_len_minus2 in the range of 0 to 30, inclusive, to appearin the syntax.

The direct_dependency_type[i] [j] is used to derive the variablesNumSamplePre-dRefLayers[i], NumMotionPredRefLayers[i],SamplePredEnabledFlag[i] [j], and MotionPredEnabledFlag[i] [j].direct_dependency_type[i] [j] shall be in the range of 0 to 2,inclusive, in bitstreams conforming to this version of thisSpecification. Although the value of direct dependency type[i] [j] shallbe in the range of 0 to 2, inclusive, in this version of thisSpecification, decoders shall allow values of direct dependency type[i][j] in the range of 3 to 2³²-2, inclusive, to appear in the syntax.

The variables NumSamplePredRefLayers[i], NumMotionPredRefLayers[i],Sam-plePredEnabledFlag[i] [j], MotionPredEnabledFlag[i] [j],NumDirectRefLayers[i], DirectRefLayerIdx[] [j], RefLayerId[i] [j],MotionPredRefLayerId[i] [j], and SamplePredRefLayerId[i] [j] are derivedas follows:

 for( i = 0; i < 64; i++ ) {   NumSamplePredRefLayers[ i ] = 0  NumMotionPredRefLayers[ i ] = 0   NumDirectRefLayers[ i ] = 0   for( j= 0; j < 64; j++ ) {     SamplePredEnabledFlag[ i ][ j ] = 0    MotionPredEnabledFlag[ i ][ j ] = 0     RefLayerId[ i ][ j ] = 0    SamplePredRefLayerId[ i ][ j ] = 0     MotionPredRefLayerId[ i ][ j] = 0   } }  for( i = 1; i <= vps_max_layers_minus1; i++ ) {   iNuhLId =layer_id_in_nuh[ i ]   for( j = 0; j < i; j++ )    if(direct_dependency_flag[ i ][ j ] ) {       DirectRefLayerIdx[ iNuhLid ][layer_id_in_nuh[ j ] ] =  NumDirectRefLayers[ iNuhLId ]      RefLayerId[ iNuhLId ][ NumDirectRefLayers-  [ iNuhLId ]++ ] =layer_id_in_nuh[ j ]         SamplePredEnabledFlag[ iNuhLId ][ j ] =  (( direct_dependency_type[ i ][ j ] + 1 ) & 1 )        NumSamplePredRefLayers[ iNuhLId ] +=  SamplePredEnabledFlag[iNuhLId ][ j ]         MotionPredEnabledFlag[ iNuhLId ][ j ] =  ( ( (direct_dependency_type[ i ][ j ] + 1 ) & 2 ) >> 1 )        NumMotionPredRefLayers[ iNuhLId ] +=  MotionPredEnabledFlag[iNuhLId ][ j ]       }  }  for( i = 1, mldx = 0, sldx = 0; i <=vps_max_layers_minus1; i++ ) {      iNuhLId = layer_id_in_nuh[ i ]     for( j = 0, j < i; j++ ) {       if( MotionPredEnabledFlag[ iNuhLId][ j ] )         MotionPredRefLayerId[ iNuhLId ][ mldx++ ] = layer_id_in_nuh[ j ]       if( SamplePredEnabledFlag[ INuhLid ][ j ] )        SamplePredRefLayerId[ iNuhLid ][ sldx++ ] =  layer_id_in_nuh[ j]      }  }

The direct_dependency_flag[i] [j], direct_dep_type_len_minus2,direct_dependency_type[i] [j] are included in the vps extension syntaxillustrated in FIG. 20A and FIG. 20B, which is included by reference inthe VPS syntax which provides syntax for the coded video sequence.

It is typically desirable to reduce the number of referenced layers thatneed to be signaled within the bitstream, and other syntax elementswithin the slice segment header may be used to effectuate such areduction. The other syntax elements may includeinter_layer_pred_enabled_flag, num_inter_layer_ref_pics_minus1, and/orinter_layer_pred_layer_idc[i]. These syntax elements may be signaled inslice segment header.

The inter_layer_pred_enabled_flag equal to 1 specifies that inter-layerprediction may be used in decoding of the current picture. Theinter_layer_pred_enabled_flag equal to 0 specifies that inter-layerprediction is not used in decoding of the current picture. When notpresent, the value of inter layer pred enabled flag is inferred to beequal to 0.

The num_inter_layer_ref_pics_minus1 plus 1 specifies the number ofpictures that may be used in decoding of the current picture forinter-layer prediction. The length of thenum_inter_layer_ref_pics_minus1 syntax element isCeil(Log2(NumDirectRefLayers[nuh_layer_id_1])) bits. The value ofnum_inter_layer_ref_pics_minus1 shall be in the range of 0 toNumDirectRefLayers[nuh_layer_id]−1, inclusive.

The variable NumActiveRefLayerPics is derived as follows:

 if( nuh_layer_id = = 0 | | NumDirectRefLayers[ nuh_layer_id ] = = 0  || !inter_layer_pred_enabled_flag )   NumActiveRefLayerPics = 0  else if(max_one_active_ref_layer_flag | |  NumDirectRefLayers[ nuh_layer_id ] == 1 )   NumActiveRefLayerPics = 1  else   NumActiveRefLayerPics =num_inter_layer_ref_pics_minus1 + 1 All slices of a coded picture shallhave the same value of NumActiveRefLayerPics.

The inter_layer_pred_layer_idc[i] specifies the variable,RefPicLayerId[i], rep-resenting the nuh_layer_id of the i-th picturethat may be used by the current picture for inter-layer prediction. Thelength of the syntax element inter_layer_pred_layer_idc[i] isCeil(Log2(NumDirectRefLayers[nuh_layer_id])) bits. The value ofinter_layer_pred_layer_idc[i] may be in the range of 0 toNumDirectRefLayers[nuh_layer_id]−1, inclusive. When not present, thevalue of inter_layer_pred_layer_idc[i] is inferred to be equal to 0.

By way of example, the system may signal various syntax elementsespecially the direct_dependency_flag[i] [j] in VPS which results in theinter-layer reference picture set for layer 3 to be [2, 0]. Then thesystem may refine further the inter-layer reference picture set with theuse of the additional syntax elements for example syntax elements inslice segment header as [2], may refine further the inter-layerreference picture set with the use of the additional syntax elements as[0], or may refine further the inter-layer reference picture set withthe use of the additional syntax elements as [ ] which is the null set.However, depending on the design of the encoder, the reference pictureset of [2, 0] may be signaled as [2, 0].

Referring to FIG. 21, the slice segment header may be modified toinclude a comparison between the numer of direct reference layers for aparticular layer (NumDirectRefLayers[num_layer_id] in the syntax) andthe number of active reference layers for the same particular layer(NumActiveRefLayerPics in the syntax). In particular, this may besignaled as“if(NumActiveRefLayerPics!=NumDirectRefLayers[nuh_layer_id])”. Thus, ifboth of these indicate the same number of layers, then there is no needto signal inter_layer_pred_layer_idc[i] in the bitstream, but may ratherdetermine/infer such values based on other syntax elements alreadysignaled.

Referring to FIG. 22, the slice segment header signalling may bemodified in a similar manner to FIG. 21 to infer the values for theinter_layer_pred_layer_idc[i] by not signalling them.

If NumActiveRefLayerPics is equal to NumDirectRefLayers[nuh_layer_id],then the value of inter_layer_pred_layer_idc[i] may be inferred asfollows.

for( i = 0; i < NumActiveRefLayerPics; i++)   inter_layer_pred_layer_idc[ i ] = i;

When not present and when NumActiveRefLayerPics is not equal toNumDirectRefLayers[nuh_layer_id], the value ofinter_layer_pred_layer_idc[i] is inferred to be equal to 0.

] When i is greater than 0, inter_layer_pred_layer_idc[i] may be greaterthan inter_layer_pred_layer_idc[i−1].

The variables RefPicLayerId[i] for each value of i in the range of 0 toNumActiveRefLayerPics−1, inclusive, NumActiveMotionPredRefLayers, andActiveMotionPredRefLayerId[j] for each value of j in the range of 0 toNumActiveMotionPre-dRefLayers−1, inclusive, maybe derived as follows:

  for( i = 0, j = 0; i < NumActiveRefLayerPics; i++)     RefPicLayerId[i ] = RefLayerId[ nuh_layer_id ][ inter_layer_pred_layer_idc[ i ] ]  if( MotionPredEnabledFlag[ nuh_layer_id ] [inter_layer_pred_layer_idc[ i ] ])       ActiveMotionPredRefLayerId[ j++] = RefLayerId[ nuh_layer_id ][ inter_layer_pred_layer_idc[ i ] ]   }  NumActiveMotionPredRefLayers = j

All slices of a picture may have the same value ofinter_layer_pred_layer_idc[i] for each value of i in the range of 0 toNumActiveRefLayerPics−1, inclusive.

The max_tid_il_ref_pics plus1[i] is signaled in VPS extension.max_tid_il_ref_pics_plus1[i] equal to 0 specifies that within the CVSnon-IRAP pictures with nuh_layer_id equal to layer_id_in_nuh[i] are notused as reference for inter-layer prediction.max_tid_il_ref_pics_plus1[i] greater than 0 specifies that within theCVS pictures with nuh_layer_id equal to layer_id_in_nuh[i] andTemporalId greater than max_tid_il_ref_pics_plus1[i]−1 are not used asreference for inter-layer prediction. When not present,max_tid_il_ref_pics_plus1[i] is unspecified.

It may be a requirement of bitstream conformance that for each value ofi in the range of 0 to NumActiveRefLayerPics−1, inclusive, either of thefollowing two conditions may be true:

   The value of max_tid_il_ref_pics_plus1[ LayerIdxInVps[ RefPicLayerId[i ] ] ] is greater than TemporalId.    The values ofmax_tid_il_ref_pics_plus1[ LayerIdxInVps[ RefPicLayerId[ i ] ] ] andTemporalId are both equal to 0 and the picture in the current accessunit with nuh_layer_id equal to RefPicLayerId[ i ] is an IRAP picture.

In another embodiment It may be a requirement of bitstream conformancethat for each value of i in the range of 0 to NumActiveRefLayerPics−1,inclusive, either of the following two conditions may be true:

   The value of max_tid_il_ref_pics_plus1[ LayerIdxInVps[ RefPicLayerId[i ] ] ] is greater than TemporalId of the picture in the current accessunit with nuh_layer_id equal to RefPicLayerId[ i ].    The values ofmax_tid_il_ref_pics_plus1[ LayerIdxInVps[ RefPicLayerId[ i ] ] ] isequal to 0 and the picture in the current access unit with nuh_layer_idequal to RefPicLayerId[ i ] is an IRAP picture.

It may be a requirement of bitstream conformance that for each value ofi in the range of 0 to NumActiveRefLayerPic31 1, inclusive, the value ofSamplePredEnabledFlag[nuh_layer_id] [RefPicLayerId[i]] orMotionPredEnabledFlag[nuh_layer_id] [RefPicLayerId[i]] shall be equal to1.

Referring to FIG. 23, another embodiment for signaling slice segmentheader is illustrated.

For the embodiment illustrated in FIG. 23, aninter_layer_pred_layer_mask[i] equal to 1 specifies that layerRefLayerId[nuh_layer_id] [i], may be used by the current picture forinter-layer prediction. The inter layer_pred_layer_mask[i] equal to 0specifies that layer RefLayerId[nuh_layer_id] [i], is not used by thecurrent picture for inter-layer prediction.

When not present the value of inter layer_pred_layer_mask[i] is inferredto be equal to 0.

The variables RefPicLayerId[i] for each value of i in the range of 0 toNumActiveRefLayerPics−1, inclusive, NumActiveMotionPredRefLayers, andActiveMotion-PredRefLayerId[j] for each value of j in the range of 0 toNumActiveMotionPre-dRefLayers−1, inclusive, are derived as follows:

  for( i = 0, j = 0, k=0; i < NumDirectRefLayers[ nuh_layer_id ]; i++)    if(inter_layer_pred_layer_mask[ i])       RefPicLayerId[ k++ ] =RefLayerId[ nuh_layer_id ][ i ]     if( MotionPredEnabledFlag[nuh_layer_id ][ i ] )       ActiveMotionPredRefLayerId[ j++ ]=RefLayerId[ nuh_layer_id ][ i ]   }   NumActiveMotionPredRefLayers = j

All slices of a picture may have the same value ofinter_layer_pred_layer_mask[i] for each value of i in the range of 0 toNumDirectRefLayers[nuh_layer_id]−1, inclusive.

It may be a requirement of bitstream conformance that for each value ofi in the range of 0 to NumActiveRefLayerPics−1, inclusive, either of thefollowing two conditions shall be true:

   The value of max_tid_il_ref_pics_plus1[ LayerIdxInVps[ RefPicLayerId[i ] ] ] is greater than TemporalId.       The values of   max_tid_il_ref_pics_plus1[ LayerIdxInVps[ RefPicLayerId[ i ] ] ]   and TemporalId are both equal to 0 and the picture in the current   access unit with nuh_layer_id equal to RefPicLayerId[ i ] is an   IRAP picture.

It may be a requirement of bitstream conformance that for each value ofi in the range of 0 to NumActiveRefLayerPics−1, inclusive, the value ofSamplePredEnabledFlag[nuh_layer_id] [RefPicLayerId[i]] orMotionPredEnabledFlag[nuh_layer_id] [RefPicLayerId[i] may be equal to 1.

It is shown in FIG. 23 that the inter_layer_pred_layer_mask[i] may besigned with u(1) which uses 1 bit, and FIG. 22 which signalsinter_layer_pred_layer_idc[i] may be signed with u(v) which may usemultiple bits. In an embodiment inter_layer_pred_layer_mask[i] issignaled instead of intra_layer_pred_idc[i]

Referring to FIG. 24, it is desirable to define profiles where thecomplexity of the system is reduced by limiting the permittedreferencing interrelationships between the different layers (e.g., baselayer and/enhancement layers). In general, the sytanx structure permitsone layer to reference multiple other layers, which results in arelatively high decoder complexity and also high encoder complexity. Ifdesired, a modified syntax structure may be used for profiles of areduced complexity where the syntax structure permits one layer toreference at most only one other layer. This limitation on the syntaxstructure may be signaled by setting a max one active ref layer flagbeing set to 1.

The max_one_active_ref_layer_flag is signaled in VPS extension.max_one_active_ref_layer_flag equal to 1 specifies that at most onepicture is used for inter-layer prediction for each picture in the CVS.max_one_active_ref_layer_flag equal to 0 specifies that more than onepicture may be used for inter-layer prediction for each picture in theCVS.

vps_max_layers_minus1 plus 1 specifies the maximum allowed number oflayers in the CVS. vps_max_layers_minus1 shall be less than 63 inbitstreams conforming to this version of this Specification. The valueof 63 for vps_max_layers_minus1 is reserved for future use byITU-T|ISO/IEC. Although the value of vps_max_layers_minus1 is requiredto be less than 63 in this version of this Specification, decoders shallallow a value of vps_max_layers_minus1 equal to 63 to appear in thesyntax. In a future super multiview coding extension of thisspecification, the value of 63 for vps_max_layers_minus1 will be used toindicate an extended number of layers.

The variable MaxLayersMinus1 is set equal to Min(62,vps_max_layers_minus1). In this document the variable MaxLayersMinus1and syntax element vps_max_layers_minus1 may be used interchangeably.Both of them maybe used to denote the same thing.

The layer_id_in_nuh[i] is signaled in VPS extension. layer_id_in_nuh[i]specifies the value of the nuh_layer_id syntax element in VCL NAL unitsof the i-th layer. For i in a range from 0 to MaxLayersMinus1,inclusive, when not present, the value of layer_id_in_nuh[i] is inferredto be equal to i. When i is greater than 0, layer_id_in_nuh[i] shall begreater than layer_id_in_nuh[31 1]. For i from 0 to MaxLayersMinus1,inclusive, the variable LayerIdxInVps[layer_id_in_nuh[i]] is set equalto i.

A bitstream constraint may be included in the case where only one directreference layer for a layer is used or at most one picture is used forinter-layer prediction for each picture in CVS, such as follows:

   In one choice, it may a requirement of the bitstream conformance thatif NumDirectRefLayers[layer_id_in_nuh[ i ]] is equal to 1 for each layeri=1,...vps_max_layers_minus1 then max_one_active_ref_layer_flag is equalto 1.    In another choice,    Let   for(i=1;i<=vps_max_layers_minus1,i++)      for(j=0,NumDirDepFlags[i]=0;j<i;j++)          NumDirDepFlags[i]+=         direct_dependency_flag[i][j];    It may be a requirement of thebitstream conformance that if NumDirDepFlags[i] is equal to 1 for eachlayer i=1,...vps_max_layers_minus1 then max_one_active_ref_layer_flag isequal to 1.

In another embodiment, it is desirable to not support the ability tosignal an inter-layer reference picture from different direct dependentlayers for each picture when max_one_active_ref_layer_flag is set equalto 1. This embodiment results in lower complexity for decoding an outputlayer set. In this embodiment the bitstream constraint proposed belowrelated to NumDirectRefLayers being equal to 1 may be required to beobeyed:

   In one choice, it is a requirement of the bitstream conformance thatif max_one_active_ref_layer_flag is equal to 1 thenNumDirectRefLayers[layer_id_in_nuh[ i ]] is equal to 1 for each layeri=1,...vps_max_layers_minus1.    In another choice,    let   for(i=1;i<=vps_max_layers_minus1,i++)      for(j=0,NumDirDepFlags[i]=0;j<i;j++)          NumDirDepFlags[i]+=         direct_dependency_flag[i][j];    It may be a requirement of thebitstream conformance that if max_one_active_ref_layer_flag is equal to1 then NumDirDepFlags[i] is equal to 1 for i=1,...vps_max_layers_minus1.

Another embodiment may include a gating flag controlled in a parameterset (e.g. pps, sps, and/or vps) to conditionally signal selected syntaxelements in the slice header related to inter-layer predictionsignalling.

Referring to FIG. 25, for example, the syntax elementsinter_layer_pred_enabled_flag, num_inter_layer_ref_pics_minus1, and/orinter_layer_pred_layer_idc[i] are signaled in slice segment header onlyif a ilp_slice_signaling_enabled_flag is equal to 1. Thusilp_slice_signaling_enabled_flag is a gating flag.

Referring to FIG. 26, and FIG. 26A the ilp_slice_signaling_enabled_flagmay be signaled in a parameter set such as in video parameter set.Referring to FIG. 27, the ilp_slice_signaling_enabled_flag may besignaled in a parameter set such as in sequence parameter set. Referringto FIG. 28, the ilp_slice_signaling_enabled_flag may be signaled in aparameter set such as in the picture parameter set. Theilp_slice_signaling_enabled_flag may be signaled in another location ofthe bitstream, as desired. In each of these parameters sets theilp_slice_signaling_enabled_flag may be sent in any location differentthan that shown in that illustrated.

The ilp_slice_signaling_enabled_flag equal to 1 specifies thatinter_layer_pred_enabled_flag, num_inter_layer_ref_pics_minus1,inter_layer_pred_layer_idc[i] are present in the slice segment headers.ilp_slice_signaling_enabled_flag equal to 0 specifies thatinter_layer_pred_enabled_flag, num_inter_layer_ref_pics minus1,inter_layer_pred_layer_idc[i] are not present in the slice segmentheader.

In some embodiments ilp_slice_signaling_enabled_flag may be insteadcalled ilp_slice_signaling_present_flag.

When ilp_slice_signaling_enabled_flag is equal to 1 inter layer predenabled flag, num_inter_layer_ref_pics_minus1,inter_layer_pred_layer_idc[i] and NumActiveRefLayersPics values areinferred as follows:

   NumActiveRefLayerPics is inferred as follows:   NumActiveRefLayerPics = NumDirectRefLayers[ nuh_layer_id ]   inter_layer_pred_layer_idc[i] is inferred as follows:       for( i =0; i < NumActiveRefLayerPics; i++)          inter_layer_pred_layer_idc[i ] = i;    num_inter_layer_ref_pics_minus1 is inferred to be equal toNumDirectRefLayers[ nuh_layer_id ] −1.    inter_layer_pred_enabled_flagis inferred to be equal to 1.

In another embodiment one or more of the syntax elements may be signaledusing a known fixed number of bits instead of u(v) instead of ue(v). Forexample they could be signaled using u(8) or u(16) or u(32) or u(64),etc.

In another embodiment one or more of these syntax element could besignaled with ue(v) or some other coding scheme instead of fixed numberof bits such as u(v) coding.

In another embodiment the names of various syntax elements and theirsemantics may be altered by adding a plus1 or plus2 or by subtracting aminus1 or a minus2 compared to the described syntax and semantics.

In yet another embodiment various syntax elements may be signaled perpicture anywhere in the bitstream. For example they may be signaled inslice segment header, pps/sps/vps/or any other parameter set or othernormative part of the bitstream.

Referring to FIG. 29, the video may include temporal sub-layer supportspecified by a temporal identifier in the NAL unit header, whichindicates a level in a hierarchical temporal prediction structure. Thenumber of decoded temporal sublayers can be adjusted during the decodingprocess of one coded video sequence. Different layers may have differentnumber of sub-layers. For example, in FIG. 29 the base layer may include3 temporal sub-layers, namely, TemporalId 0, TemporalId 1, TemporalId 2.For example, the enhancement layer 1 may include 4 temporal sub-layers,namely, TemporalId 0, TemporalId 1, TemporalId 2, and TemporalId 3. Theaccess unit may be defined as a set of NAL units that are associatedwith each other according to a specified classification rule, areconsecutive in decoding order, and/or contain the VCL NAL units of allcoded pictures associated with the same output time (picture order countor otherwise) and their associated non-VCL NAL units.

In FIG. 29 base layer has a lower overall frame rate compared to theenhancement layer 1. For example the frame rate of the base layer may be30 Hz or 30 frames per second. The frame rate of the enhancement layer 1may be 60 Hz or 60 frames per second. In FIG. 29 at some output times anaccess unit may contain a coded picture of base layer and a codedpicture of enhancement layer 1 (e.g. access unit Y in FIG. 29). In FIG.29 at some output times an access unit may contain only a coded pictureof enhancement layer 1 (e.g. access unit X in FIG. 29).

As previously described, the dependency of one layer on one or moreother layers may be signaled in the VPS for a sequence. In addition ateach slice within a respective layer, the slice segment header syntaxpermits a further refinement of this dependency by removing one or moreof the dependencies for the respective slice. For example, the layerdependency in the VPS may indicate that layer 3 is dependent on layer 2and base layer 0. For example, a slice in layer 3 may further modifythis dependency to remove the dependency on layer 2.

Referring to FIGS. 30A-30D, a slice segment header(slice_segment_header), includes a syntax structure that facilitates theidentification of dependencies, a portion of which is excerpted below.

if( nuh_layer_id > 0 && all_ref_layers_active_flag &&NumDirectRefLayers[ nuh_layer_id ] > 0) {  inter_layer_pred_enabled_flagu(1)  if( inter_layer_pred_enabled_flag &&  NumDirectRefLayers[nuh_layer_id ] > 1) {   if( !max_one_active_ref_layer_flag )   num_inter_layer_ref_pics_minus1 u(v)   if( NumActiveRefLayerPics !=  NumDirectRefLayers[ nuh_layer_id ] )    for( i = 0; i <NumActiveRefLayerPics; i++ )     inter_layer_pred_layer_idc[ i ] u(v)  }}

In an example case a base layer has coded pictures at a rate of 30 hertzand an enhancement layer has coded pictures at a rate of 60 hertz, whereevery other coded picture of the enhancement layer are not aligned withthe coded pictures of the base layer. This scenarios is similar to theFIG. 29. Also, it is noted that in general each coded picture of theenhancement layer may not include a corresponding coded picture in thebase layer. In some cases, there may be some corresponding codedpictures in the base layer with coded pictures of the enhancement layer.Unfortunately, this syntax structure does not permit discriminationbetween the case where a coded picture of the base layer is not presentin an access unit in the original bitstream (e.g. access unit X in FIG.29) and the case where a coded picture of the base layer was present inan access unit in the original bitstream but has been lost duringtransmission. In this manner, the decoder does not know if the codedpicture of the base layer has been lost (i.e. a lost picture) or whetherthere was no coded picture of the base layer in the first place (i.e. anon-existing base layer picture).

It was determined that even with the syntax illustrated in FIGS.30A-30D, there are conditions where the system can not signal theremoval of a layer in the slice segment header. Under such conditionsthe decoder is not able to distinguish between the case that an AU hadno coded picture for a direct reference layer of a current layer due tothat picture not existing in the bitstream (due to the reference layerhaving different frame rate) versus the case that the coded picture forthe direct reference layer of a current layer was lost duringtransmission. The particular conditions include three conditions,namely, when max_one_active_ref_layer_flag is equal to 1,NumDirectRefLayers[nuh_layer_id] is equal to 1, and/or allref_layers_active_flag is equal to 1. For each of these conditions a “Noreference picture” would be inferred during the decoding process for theinter-layer reference picture set even when base layer (i.e. referencelayer) did not have a picture in the original bitstream. This isincorrect and no-optimal behavior. In some cases in this scenario anunavailable reference picture would be rgeated for such a “no referencepicture” and would be used as the base layer (i.e. reference layer)picture thus resulting in incorrect operation.

To alleviate this limitation, it was determined that it is desirable tosignal the maximum number of temporal sub-layers for each layer in theSHVC and/or MV-HEVC. This signaling may be achieved in any suitablemanner. A first technique for signing the maximum number of temporalsub-layers for each layer is by always explicity signaling the maximumnumber for each layer. A second technique for signaling the maximumnumber of temporal sub-layers for each layer is signaled conditioned ona presence flag. In a third technique for signaling the maximum numberof temporal sub-layers for each layer is coded predictively with respectto the maximum number of temporal sub-layers for the previous layer byconditioning them on a presence flag. Also, the semantics of the slicesegment header syntax elements num_inter_layer_ref_pics_minus1 and interlayer pred layer idc[i] and the derivation of NumActiveRefLayerPics maybe modified based upon the signaling of the temporal sub-layerinformation for each layer. Additionally, or alternatively alayer_present_in_au_flag[i] may be signaled for NumActiveRefLayerPics inthe slice segment header, to similarly disambiguate between lost picturecase and non-existing picture case.

Referring to FIG. 31, a modified vps_expension( ) syntax may includeexplicity signaling the maximum number temporal sub-layers that may bepresent for each layer, as opposed to the bitstream as a whole. In thismanner, two different layers may each have a different maximum number oftemporal sublayers. In particular the sub_layers_vps_max_minus1[i] plus1 specifies the maximum number of temporal sub-layers that may bepresent in the CVS for layer with nuh_layer_id equal tolayer_id_in_nuh[i]. The value of sub_layers_vps_max_minus1[i] shall bein the range of 0 to vps_max_sub_layers_minus1 inclusive. When notpresent sub_layers_vps_max_minus1[i] shall be equal to vps max sublayers minusl. Alternatively, the value of sub_layers_vps_max_minus1[i]may be in the range of 0 to 6 inclusive. Alternatively, the value ofsub_layers_vps_max_minus1[i] may only be signaled for the enhancementlayers in the VPS extension as illustrated in FIG. 32.

Referring to FIG. 33, a modified vps_expension( ) syntax may includesignaling the maximum number for each layer conditioned on a presenceflag. In this manner, two different layers may each have a differentmaximum number of temporal sublayers. In particular thesub_layers_vps_max_minus1_present_flag equal to 1 specifies that thesyntax elements sub_layers_vps_max_minus1[i] are present. Thesub_layers_vps_max_minus1 present flag equal to 0 specifies that thesyntax elements sub_layers_vps_max_minus1[i] are not present. Thesub_layers_vps_max_minus1[i] plus 1 specifies the maximum number oftemporal sub-layers that may be present in the CVS for layer withnuh_layer_id equal to layer_id_in_nuh[i]. The value ofsub_layers_vps_max_minus1[i] shall be in the range of 0 to vps max sublayers minus1 inclusive. When not present sub_layers_vps_max_minus1[i]shall be equal to vps_max_sub_layers_minusl. Alternatively, the value ofsub_layers_vps_max_minus1[i] may be in the range of 0 to 6 inclusive.Alternatively, the value of sub_layers_vps_max_minus1[i] may only besignaled for the enhancement layers in the VPS extension as illustratedin FIG. 34. Referring to FIG. 35, a modified vps_expension( ) syntax mayinclude signaling the maximum number of temporal sub-layers for eachlayer by coding them predictively with respect to the maximum number oftemporal sub-layers for the previous layer by conditioning them on apresence flag. In this manner, two different layers may each have adifferent maximum number of temporal sublayers. In particular thesub_layers_vps_max_minus1 predict flag[i] equal to 1 specifies thatsub_layers_vps_max_minus1[i] is inferred to be equal tosub_layers_vps_max_minus1 [i 1]. The sub_layers_vps_max_minus1predict_flag[i ]equal to 0 specifies that sub_layers _vps_max_minus1[i]is explicitly signaled. The value of sub_layers_vps_max_minus1 predictflag[0] is inferred to be equal to 0. The sub_layers_vps_max_minus1[i]plus 1 specifies the maximum number of temporal sub-layers that may bepresent in the CVS for layer with nuh_layer_id equal tolayer_id_in_nuh[i]. The value of sub_layers_vps_max_minus1[i] shall bein the range of 0 to vps_max_sub_layers_minus1 inclusive. Whensub_layers_vps_max_minus1_predict_flag[i] is equal to 1,sub_layers_vps_max_minus1[i] is inferred to be equal tosub_layers_vps_max_minus1[i−1]. The value ofsub_layers_vps_max_minus1[09 is inferred to be equal tovps_max_sub_layers_minus1. Alternatively, the value ofsub_layers_vps_max_minus1[i] may be in the range of 0 to 6 inclusive.Alternatively, the value of sub_layers_vps_max_minus1[i] may only besignaled for the enhancement layers in the VPS extension as illustratedin FIG. 36.

The slice segment headers may be modified, such as described below, insuch a manner that the derivation of the NumActiveRefLayerPics accountsfor the occurrence of one of the aforementioned three conditions so asto reduce the ambiguity using the signaled information about the maximumnumber of temporal sub-layers that may be present for each layer.

The inter_layer_pred_enabled_flag equal to 1 specifies that inter-layerprediction may be used in decoding of the current picture. Theinter_layer_pred_enabled_flag equal to 0 specifies that inter-layerprediction is not used in decoding of the current picture. Thenum_inter_layer_ref_pics_minus1 plus 1 specifies the number of picturesthat may be used in decoding of the current picture for inter-layerprediction. The length of the num_inter_layer_ref_pics_minus1 syntaxelement is Ceil(Log2(NumDirectRefLayers[nuh_layer_id])) bits. The valueof num_inter_layer_ref_pics_minus1 shall be in the range of 0 toNumDirectRefLayers[nuh_layer_id]−1, inclusive. The variableNumActiveRefLayerPics is derived as follows:

  if( nuh_layer_id = = 0 || NumDirectRefLayers[ nuh_layer_id ] = = 0 )    NumActiveRefLayerPics = 0   else if( all_ref_layers_active_flag ){    NumActiveRefLayerPics = NumDirectRefLayers[ nuh_layer_id ]     for(i = 0; i < NumDirectRefLayers[ nuh_layer_id ]; i++) {       if(sub_layers_vps_max_minus1[ LayerIdxInVps[ RefLayer[ nuh_layer_id ]     [i ] ] ] < TemporalId )       NumActiveRefLayerPics =NumActiveRefLayerPics − 1     }   }   else if(linter_layer_pred_enabled_flag )     NumActiveRefLayerPics = 0   elseif( max_one_active_ref_layer_flag || NumDirectRefLayers[ nuh_layer_id ]= = 1 ) {     if( sub_layers_vps_max_minus1[ LayerIdxInVps[ RefLayer[nuh_layer_id ]   [ 0 ] ] ] < TemporalId )       NumActiveRefLayerPics =0     else       NumActiveRefLayerPics = 1   }   else    NumActiveRefLayerPics = num_inter_layer_ref_pics_minus1 + 1

All slices of a coded picture shall have the same value ofNumActiveRefLayerPics. The inter_layer_pred_layer_idc[i] specifies thevariable, RefPicLayerId[i], representing the nuh_layer_id of the i-thpicture that may be used by the current picture for inter-layerprediction. The length of the syntax elementinter_layer_pred_layer_idc[i] isCeil(Log2(NumDirectRefLayers[nuh_layer_id [)) bits. The value ofinter_layer_pred_layer_idc[i] shall be in the range of 0 toNumDirectRefLayers[nuh_layer_id]−1, inclusive. When not present, thevalue of inter_layer_pred_layer_idc[i] is inferred as follows:

for( i = 0, j = 0; i < NumDirectRefLayers[ nuh_layer_id ]; i++) {    if( sub_layers_vps_max_rninus1[ LayerIdxInVps[ RefLayer   [nuh_layer_id ][ i ] ] ] >= TemporalId )      inter_layer_pred_layer_idc[ j++ ] = i;   }   In a variantembodiment when not present, the value of inter_layer_pred_layer_idc[ i] is inferred as follows:   for( i = 0, j = 0; i < NumDirectRefLayers[nuh_layer_id ]; i++) {     if( sub_layers_vps_max_minus1[ LayerIdxInVps[RefLayer   [ nuh_layer_id ][ i ] ] ] < TemporalId )      inter_layer_pred_layer_idc[j++ ] = i;   }

When i is greater than 0, inter_layer_pred_layer_idc[i] shall be greaterthan inter_layer_pred_layer_idc[i−1]. The variables RefPicLayerId[i] forall values of i in the range of 0 to NumActiveRefLayerPics—1, inclusive,are derived as follows:

   for( i = 0, j = 0; i < NumActiveRefLayerPics; i++)      RefPicLayerId[ i ] = RefLayerId[ nuh_layer_id ][inter_layer_pred_layer_idc[ i ] ]

All slices of a picture shall have the same value ofinter_layer_pred_layer_idc[i] for each value of i in the range of 0 toNumActiveRefLayerPics−1, inclusive. It is a requirement of bitstreamconformance that for each value of i in the range of 0 toNumActiveRefLayerPics−1, inclusive, either of the following twoconditions shall be true:

   (1) The value of max_tid_il_ref_pics_plus1[ LayerdxInVps[RefPicLayerId[ i ] ] ] is greater than TemporalId.     (2)  The valuesof max_tid_il_ref_pics_plus1[ LayerIdxInVps[ RefPicLayerId[ i ] ] ] andTemporalId are both equal to 0 and the picture in the current accessunit with nuh_layer_id equal to RefPicLayerId[ i ] is an IRAP picture.

In another embodiment the names of various syntax elements and theirsemantics may be altered by adding a plus1 or plus2 or by subtracting aminus1 or a minus2 compared to the described syntax and semantics.

In another embodiment some of the conditions in the if statements may bealtered by adding a plus 1 or plus2 or by subtracting a minus1 or aminus2 compared to the described syntax.

Referring to FIG. 37, an additional signaling technique involvessignaling a layer_present_in_au_flag[i]. The layer_present_in_au_flag[i]equal to 1 specifies that a picture with nuh_layer_id equal toRefPicLayerId[i] is present in the current access unit. Thelayer_present_in_au_flag[i] equal to 0 specifies that a picture withnuh_layer_id equal to RefPicLayerId[i] is not present in the currentaccess unit. When not present layer_present_in_au_flag[i] is inferred tobe equal to 1.

Referring to FIG. 38, an additional signaling technique involvessignaling the layer_present_in_au_flag[i]. Thelayer_present_in_au_flag[i] equal to 1 specifies that a picture withnuh_layer_id equal to RefLayerId[nuh_layer_id] [i] is present in thecurrent access unit. The layer_present_in_au_flag[i] equal to 0specifies that a picture with nuh_layer_id equal toRefLayerId[nuh_layer_id] [i] is not present in the current access unit.When not present layer_present_in_au_flag[i] is inferred to be equal to1.

Referring to FIG. 39, an additional signaling technique involvessignaling the layer_present_in_au_flag[i]. Thelayer_present_in_au_flag[i] equal to 1 specifies that a picture withnuh_layer_id equal to layer_id_in_nuh[i] is present in the currentaccess unit. layer_present_in_au_flag[i] equal to 0 specifies that apicture with nuh_layer_id equal to layer_id_in_nuh[i] is not present inthe current access unit. When not present layer_present_in_au_flag[i] isinferred to be equal to 1.

If desired, the flags layer_present_in_au_flag[i] may be only signaledin FIG. 37, FIG. 38, and/or FIG. 39 if one or more of the followingconditions are met.

The first condition is that if only one active reference layer can beused for each layer (i.e. max_one_active_ref_layer_flag is equal to 1).

The second condition is that the number of direct reference layers for alayer as signaled by direct dependency relationship between layers (e.g.by direct_dependency_flag[i][j]) is equal to 1 (i.e.NumDirectRefLayers[nuh_layer_id] is equal to 1).

The third condition is that all the direct reference layers for a layeras signaled by direct dependency relationship between layers (e.g. bydirect_dependency_flag[i] [j]) is equal to 1 are active reference layersfor the coded picture of the layer (e.g. all_ref_layers_active_flag isequal to 1).

The three variants shown in FIG. 40, FIG. 41, and FIG. 42 for the abovethree conditions corresponds respectively to FIG. 37, FIG. 38, and FIG.39.

Referring to FIG. 43, the decoding process for the inter-layer referencepicture set may be modified. The outputs of this process are updatedlists of inter-layer reference pictures RefPicSetInterLayer0 andRefPicSetInterLayer1 and the variables NumActiveRefLayerPics0 andNumActiveRefLayerPics1. The variable currLayerId is set equal tonuh_layer_id of the current decoded pictures. The listsRefPicSetInterLayer0 and RefPicSetInterLayer1 are first emptied,NumActiveRefLayerPics0 and NumActiveRefLayerPics1 are set equal to 0followed by steps as illustrated in FIG. 43. There shall be no entryequal to “no reference picture” in RefPicSetInterLayer0 orRefPicSetInterLayer1. The RefPicSetInterLayer1 is always empty since thevalue of ViewId[i] is equal to zero for all layers. If the currentpicture is a RADL picture, there shall be no entry in theRefPicSetInterLayer0 or RefPicSetInterLayer1 that is a RASL picture. Anaccess unit may contain both RASL and RADL pictures.

Referring to FIG. 44, the decoding process for the inter-layer referencepicture set may be modified. The outputs of this process are updatedlists of inter-layer reference pictures RefPicSetInterLayer0 andRefPicSetInterLayer1 and the variables NumActiveRefLayerPics0 andNumActiveRefLayerPics1. The variable currLayerId is set equal tonuh_layer_id of the current decoded picture. The listsRefPicSetInterLayer0 and RefPicSetInterLayer1 are first emptied,NumActiveRefLayerPics0 and NumActiveRefLayerPics1 are set equal to 0followed by steps as illustrated in FIG. 44. There shall be no entryequal to “no reference picture” in RefPicSetInterLayer0 orRefPicSetInterLayer1. The RefPicSetInterLayer1 is always empty since thevalue of ViewId[i] is equal to zero for all layers. If the currentpicture is a RADL picture, there shall be no entry in theRefPicSetInterLayer0 or RefPicSetInterLayer1 that is a RASL picture. Anaccess unit may contain both RASL and RADL pictures.

Referring to FIG. 45, the decoding process for the inter-layer referencepicture set may be modified. The outputs of this process are updatedlists of inter-layer reference pictures RefPicSetInterLayer0 andRefPicSetInterLayer1 and the variables NumActiveRefLayerPics0 andNumActiveRefLayerPics1. The variable currLayerId is set equal tonuh_layer_id of the current decoded picture. The listsRefPicSetInterLayer0 and RefPicSetInterLayer1 are first emptied,NumActiveRefLayerPics0 and NumActiveRefLayerPics1 are set equal to 0followed by steps as illustrated in FIG. 45. There shall be no entryequal to “no reference picture” in RefPicSetInterLayer0 orRefPicSetInterLayer1. The RefPicSetInterLayer1 is always empty since thevalue of ViewId[i] is equal to zero for all layers. If the currentpicture is a RADL picture, there shall be no entry in theRefPicSetInterLayer0 or RefPicSetInterLayer1 that is a RASL picture. Anaccess unit may contain both RASL and RADL pictures.

Referring to FIG. 46, the decoding process for the inter-layer referencepicture set may be modified. The outputs of this process are updatedlists of inter-layer reference pictures RefPicSetInterLayer0 andRefPicSetInterLayer1 and the variables NumActiveRefLayerPics0 andNumActiveRefLayerPics1. The variable currLayerId is set equal tonuh_layer_id of the current decoded picture. The listsRefPicSetInterLayer0 and RefPicSetInterLayer1 are first emptied,NumActiveRefLayerPics0 and NumActiveRefLayerPics1 are set equal to 0followed by steps as illustrated in FIG. 46. There shall be no entryequal to “no reference picture” in RefPicSetInterLayer0 orRefPicSetInterLayer1. The RefPicSetInterLayer1 is always empty since thevalue of ViewId[i] is equal to zero for all layers. If the currentpicture is a RADL picture, there shall be no entry in theRefPicSetInterLayer0 or RefPicSetInterLayer1 that is a RASL picture. Anaccess unit may contain both RASL and RADL pictures.

In an alternative embodiment the syntax for signaling inter-layerprediction information in slice segment header may be modified as shownin FIG. 47. In this case the syntax elementsinter_layer_pred_enabled_flag, num_inter_layer_ref_pics_minus1 andinter_layer_pred_layer idc[i] would be always signaled event when one ormore of the conditions as follows are true: whenmax_one_active_ref_layer_flag is equal to 1, and/orNumDirectRefLayers[nuh_layer_id] is equal to 1, and/orall_ref_layers_active_flag is equal to 1.

In this case the ambiguity about a lost reference layer picture versusnon-existing reference layer picture is removed. In this case thefollowing may apply.

The inter_layer_pred_enabled_flag equal to 1 specifies that inter-layerprediction may be used in decoding of the current picture. Theinter_layer_pred_enabled_flag equal to 0 specifies that inter-layerprediction is not used in decoding of the current picture. Thenum_inter_layer_ref_pics_minus1 plus 1 specifies the number of picturesthat may be used in decoding of the current picture for inter-layerprediction. The length of the num_inter_layer_ref_pics_minus1 syntaxelement is Ceil(Log2(NumDirectRefLayers[nuh_layer_id])) bits. The valueof num_inter_layer_ref_pics_minus1 shall be in the range of 0 toNumDirectRefLayers[nuh_layer_id]−1, inclusive. The variableNumActiveRefLayerPics is derived as follows:

if( nuh_layer_id = = 0 || NumDirectRefLayers[ nuh_layer_id ] = = 0 )  NumActiveRefLayerPics = 0 else   NumActiveRefLayerPics =num_inter_layer_ref_pics_minus1 + 1

All slices of a coded picture shall have the same value ofNumActiveRefLayerPics. The inter_layer_pred_layer_idc[i] specifies thevariable, RefPicLayerId[i], representing the nuh_layer_id of the i-thpicture that may be used by the current picture for inter-layerprediction. The length of the syntax elementinter_layer_pred_layer_idc[i] isCeil(Log2(NumDirectRefLayers[nuh_layer_id])) bits. The value ofinter_layer_pred_layer idc[i] shall be in the range of 0 toNumDirectRefLayers[nuh_layer_id]−1, inclusive. When i is greater than 0,inter layer pred layer idc[i] shall be greater thaninter_layer_pred_layer_idc[i−1 ]. The variables RefPicLayerId[i] for allvalues of i in the range of 0 to NumActiveRefLayerPics−1, inclusive, arederived as follows:

   for( i = 0, j = 0; i < NumActiveRefLayerPics; i++)      RefPicLayerId[ i ] = RefLayerId[ nuh_layer_id ][inter_layer_pred_layer_idc[ i ] ]

All slices of a picture shall have the same value ofinter_layer_pred_layer_idc[i] for each value of i in the range of 0 toNumActiveRefLayerPics−1, inclusive. It is a requirement of bitstreamconformance that for each value of i in the range of 0 toNumActiveRefLayerPics−1, inclusive, either of the following twoconditions shall be true:

   (1) The value of max_tid_il_ref_pics_plus1[ LayerIdxInVps[RefPicLayerId[ i ] ] ] is greater than TemporalId.     (2)  The valuesof max_tid_il_ref_pics_plus1[ LayerIdxInVps[ RefPicLayerId[ i ] ] ] andTemporalId are both equal to 0 and the picture in the current accessunit with nuh_layer_id equal to RefPicLayerId[ i ] is an IRAP picture.

In HEVC (JCTVC-L1003), SHVC (JCTVC-P1008) and MV-HEVC (JCT3V-G1004) itis required that the value of TemporalId shall be the same for all VCLNAL units of an access unit. The value of TemporalId of an access unitis the value of the TemporalId of the VCL NAL units of the access unit.

For HEVC an access unit is defined as a set of NAL units that areassociated with each other according to a specified classification rule,are consecutive in decoding order, and contain exactly one codedpicture.

In SHVC and MV-HEVC an access unit is defined as a set of NAL units thatare associated with each other according to a specified classificationrule, are consecutive in decoding order, and contain the VCL NAL unitsof all coded pictures associated with the same output time and theirassociated non-VCL NAL units.

In SHVC and MV-HEVC TRAP pictures are allowed to be cross-layernon-aligned. This is helpful in supporting different IRAP frequency fordifferent layers. It also allows flexible placement of IRAP pictures inany layer without requiring an IRAP picture to be coded in the sameaccess unit for other layers. However in HEVC, SHVC and MV-HEVC ifnal_unit_type is in the range of BLA_W_LP to RSV_IRAP_VCL23, inclusive,i.e. the coded slice segment belongs to an IRAP picture, TemporalIdshall be equal to 0.

Thus although in SHVC and MV-HEVC an IRAP picture could be flexiblycoded in any layer in an access unit without requiring an IRAP picturein other layers in the same access unit, it is still currently requiredthat when an IRAP picture is coded in any layer in an access unit thenall the other layers in the same access unit must have coded pictureswith TemporalId equal to 0. It is asserted that this puts unnecessaryrestrictions on the flexibility of coding structures that can besupported. For example following scenario is currently not supported inSHVC and MV-HEVC.

If a particular layer (e.g. base layer) is coded with an all intraconfiguration where each coded picture is an IRAP picture then all thecollocated pictures in those access units for all the other layers mustbe coded with TemporalId equal to 0 (either as IRAP pictures or asnon-IRAP pictures with TemporalId equal to 0) which means that thetemporal sub-layering could not be used for those pictures. Thislimitation is shown in FIG. 48. Thus with current SHVC and MV-HEVCspecification the coding configuration can only be similar to as shownin FIG. 48 where all the coded pictures of base layer are IRAP pictures.In this case all the coded pictures in the same AU for enhancement layer1 must be coded with TemporalId equal to 0.

Changes in the TemporalID alignment to support more flexible codingstructure are described below. The described changes allow the a moreflexible coding structure to be supported in SHVC and MV-HEVC. Thus withthe changes described below the coding structure as shown in FIG. 49 issupported. In FIG. 49 coding structure the base layer consists of codedpictures which are all IRAP pictures and thus have a TemporalId equal to0. But the enhancement layer 1 pictures in the same AU can be coded withTemporalId different than TemporalId 0. Thus the Enhancement layer 1picture can have a TemporalId 1 in the same AU where base layer pictureis an IRAP picture and has a TemporalId equal to 0.

The changes to achieve this flexibility in SHVC and MV-HEVC aredescribed next.

Non-intra random access point (Non-IRAP) access unit is defined as anaccess unit in which the coded picture is not an IRAP picture.

Non-intra random access point (Non-IRAP) picture is defined as a codedpicture for which each VCL NAL unit has nal_unit_type with a VCL NALunity type value other than any value in the range of BLA_W_LP toRSV_IRAP_VCL23, inclusive.

It can be noted that a non-IRAP picture is a picture which is not a BLApicture, a CRA picture or an IDR picture.

The nuh_temporal_id_plus1 minus 1 specifies a temporal identifier forthe NAL unit. The value of nuh_temporal_id_plus1 shall not be equal to0.

The variable TemporalId may be specified asTemporalId=nuh_temporal_id_plus1−1.

If nal_unit_type is in the range of BLA_W_LP to RSV_IRAP_VCL23,inclusive, i.e. the coded slice segment belongs to an IRAP picture,TemporalId shall be equal to 0. Otherwise, when nal_unit_type is equalto TSA_R, TSA_N, STSA_R, or STSA_N, TemporalId shall not be equal to 0.

The value of TemporalId shall be the same for all VCL NAL units of allnon-IRAP coded pictures in an access unit. If in an access unit all VCLNAL units have a nal_unit_type in the range of BLA_W_LP toRSV_IRAP_VCL23, inclusive, i.e. the coded slice segments belongs to anIRAP picture, the value of Temporal ID of the access unit is 0.Otherwise the value of TemporalId of an access unit is the value of theTemporalId of the VCL NAL units of non-IRAP coded pictures in the accessunit.

The value of TemporalId for non-VCL NAL units is constrained as follows:

-   -   If nal_unit_type is equal to VPS_NUT or SPS_NUT, TemporalId        shall be equal to 0 and the TemporalId of the access unit        containing the NAL unit shall be equal to 0.    -   Otherwise if nal_unit_type is equal to EOS_NUT or EOB_NUT,        TemporalId shall be equal to 0.    -   Otherwise, if nal_unit_type is equal to AUD_NUT or FD_NUT,        TemporalId shall be equal to the Temp\oralId of the access unit        containing the NAL unit.    -   Otherwise, TemporalId shall be greater than or equal to the        TemporalId of the access unit containing the NAL unit.

It can be noted that When the NAL unit is a non-VCL NAL unit, the valueof TemporalId is equal to the minimum value of the TemporalId values ofall access units to which the non-VCL NAL unit applies. Whennal_unit_type is equal to PPS_NUT, TemporalId may be greater than orequal to the TemporalId of the containing access unit, as all PPSs maybe included in the beginning of a bitstream, wherein the first codedpicture has TemporalId equal to 0. When nal_unit type is equal toPREFIX_SEI_NUT or SUFFIX_SEI_NUT, TemporalId may be greater than orequal to the TemporalId of the containing access unit, as an SEI NALunit may contain information, e.g. in a buffering period SEI message ora picture timing SEI message, that applies to a bitstream subset thatincludes access units for which the TemporalId values are greater thanthe TemporalId of the access unit containing the SEI NAL unit.

In a variant embodiment the value of TemporalId shall be the same forall VCL NAL units with nal_unit_type equal to any value except values inthe range of BLA_W_LP to RSV_IRAP_VCL23, inclusive in an access unit. Ifin an access unit all VCL NAL units have a nal_unit_type in the range ofBLA_W_LP to RSV_IRAP_VCL23, inclusive, i.e. the coded slice segmentbelongs to an IRAP picture, the value of Temporal ID of the access unitis 0. Otherwise the value of TemporalId of an access unit is the valueof the TemporalId of the VCL NAL units of non-IRAP coded pictures in theaccess unit.

In another variant embodiment the value of TemporalId shall be the samefor all

VCL NAL units with nal_unit_type equal to any value except values in therange of BLA_W_LP to RSV_IRAP_VCL23, inclusive in an access unit. Thevalue of TemporalId of an access unit is the value of the highestTemporalId of the VCL NAL units in the access unit.

In a further variant embodiment the value of TemporalId shall be thesame for all VCL NAL units of all non-IRAP coded pictures in an accessunit. The value of TemporalId of an access unit is the value of thehighest TemporalId of the VCL NAL units in the access unit.

As mentioned previously in HEVC (JCTVC-L1003), SHVC (JCTVC-P1008) andMV-HEVC (JCT3V-G1004) it is required that the value of TemporalId shallbe the same for all VCL NAL units of an access unit.

Also in HEVC, SHVC, and MV-HEVC if nal_unit_type is in the range ofBLA_W_LP to RSV_IRAP_VCL23, inclusive, i.e. the coded slice segmentbelongs to an IRAP picture, TemporalId shall be equal to 0.

It is also required that when nal_unit_type is equal to TSA_R, TSA_N,STSA_R, or STSA_N, TemporalId shall not be equal to 0.

Also in HEVC, SHVC, and MV-HEVC there are also further restrictions asfollows:

When one picture picA of a layer layerA has nal_unit_type equal to TSA_Nor TSA_R, each picture in the same access unit as picA in a direct orindirect reference layer of layerA shall have nal_unit_type equal toTSA_N or TSA_R.

When one picture picA of a layer layerA has nal_unit_type equal toSTSA_N or STSA_R, each picture in the same access unit as picA in adirect or indirect reference layer of layerA shall have nal_unit_typeequal to STSA_N or STSA_R.

Thus with all the current restrictions in HEVC, SHVC, and MV-HEVC alayer could not code a TSA or STSA picture when any other picture in thesame access unit is an IRAP picture. Also a TSA or STSA picture must becoded in this case in direct and indirect reference layers of a layer.This current limitation is shown in FIG. 50 which results in a lessflexibility in coding structure. In FIG. 50 enhancement layer 1 is usingbase layer as its direct reference layer. When a TSA picture is coded inenhancement layer l, a TSA picture must be coded in the same access unitin the base layer. Similarly when a STSA picture is coded in enhancementlayer l, a STSA picture must be coded in the same access unit in thebase layer. This limits flexibility.

In a more flexible scenario if an IDR picture could be coded in one ofthe direct or indirect reference layers and TSA or STSA picture could becoded in other layer(s) then temporal layer upswitching at that accessunit would still be supported. FIG. 51 shows such a flexible codingstructure. In coding structure in FIG. 51 when a TSA picture is coded inenhancement layer 1, a TSA picture could be coded in the same accessunit in the base layer similar to FIG. 50. This scenario is not shown inFIG. 51 but is supported. Additionally as shown in FIG. 33 at outputtime t2 when a TSA picture is coded in enhancement layer l, an IDRpicture (or in a variant embodiment an IRAP picture) could be coded inthe same access unit in the base layer. Similarly as shown in FIG. 51 atoutput time t3 when a STSA picture is coded in enhancement layer 1, anIDR picture (or in a variant embodiment an IRAP picture) could be codedin the same access unit in the base layer. Additionally in codingstructure in FIG. 51 when a STSA picture is coded in enhancement layer1, a STSA picture could be coded in the same access unit in the baselayer similar to FIG. 50. This scenario is not shown in FIG. 51 but issupported. The overall flexibility shown in FIG. 51 is currentlydisallowed by SHVC and MV-HEVC.

Changes to the alignment of TSA and STSA pictures to support moreflexible coding structure are described next. These changes allowexample coding structure shown in FIG. 51 and other similar flexiblecoding structure when using TSA and STSA pictures.

nal_unit_type specifies the type of RBSP data structure contained in theNAL unit as specified in Table 7 (1).

When one picture picA of a layer layerA has nal_unit_type equal to TSA_Nor TSA_R, each picture in the same access unit as picA in a direct orindirect reference layer of layerA shall have nal_unit_type equal toTSA_N or TSA_R or IDR_W_RADL or IDR_N_LP.

When one picture picA of a layer layerA has nal_unit_type equal toSTSA_N or STSA_R, each picture in the same access unit as picA in adirect or indirect reference layer of layerA shall have nal_unit_typeequal to STSA_N or STSA_R or IDR_W_RADL or IDR_N_LP.

In a variant embodiment: nal_unit_type specifies the type of RBSP datastructure contained in the NAL unit as specified in Table 7 (1).

When one picture picA of a layer layerA has nal_unit_type equal to TSA_Nor TSA_R, each picture in the same access unit as picA in a direct orindirect reference layer of layerA shall have nal_unit_type equal toTSA_N or TSA_R or IDR_N_LP.

When one picture picA of a layer layerA has nal_unit_type equal toSTSA_N or STSA_R, each picture in the same access unit as picA in adirect or indirect reference layer of layerA shall have nal_unit_typeequal to STSA_N or STSA_R or IDR_N_LP.

In a variant embodiment: nal_unit_type specifies the type of RBSP datastructure contained in the NAL unit as specified in Table 7 (1).

When one picture picA of a layer layerA has nal_unit_type equal to TSA_Nor TSA_R, each picture in the same access unit as picA in a direct orindirect reference layer of layerA shall have nal_unit_type equal toTSA_N or TSAR or IDR W RADL or IDR_N_LP or BLA_W_LP or BLA_W_RADL orBLA_N_LP.

When one picture picA of a layer layerA has nal_unit_type equal toSTSA_N or STSA_R, each picture in the same access unit as picA in adirect or indirect reference layer of layerA shall have nal_unit_typeequal to STSA_N or STSA_R or IDR_W_RADL or IDR_N_LP or BLA_W_LP orBLA_W_RADL or BLA_N_LP.

In a variant embodiment: nal_unit_type specifies the type of RBSP datastructure contained in the NAL unit as specified in Table 7 (1).

When one picture picA of a layer layerA has nal_unit_type equal to TSA_Nor TSA_R, each picture in the same access unit as picA in a direct orindirect reference layer of layerA shall have nal_unit_type equal toTSA_N or TSA_R or IDR_W_RADL or IDR_N_LP or BLA_W_LP or BLA_W_RADL orBLA_N_LP or CRA_NUT.

When one picture picA of a layer layerA has nal_unit_type equal toSTSA_N or STSA_R, each picture in the same access unit as picA in adirect or indirect reference layer of layerA shall have nal_unit_typeequal to STSA_N or STSA_R or IDR_W_RADL or IDR_N LP or BLA_W_LP orBLA_W_RADL or BLA_N_LP or CRA_NUT.

In a variant embodiment: nal_unit_type specifies the type of RBSP datastructure contained in the NAL unit as specified in Table 7 (1).

When one picture picA of a layer layerA has nal_unit_type equal to TSA_Nor TSA_R, each picture in the same access unit as picA in a direct orindirect reference layer of layerA shall have nal_unit_type equal toTSA_N or TSA_R or nal_unit_type is in the range of BLA_W_LP toRSV_IRAP_VCL23, inclusive.

When one picture picA of a layer layerA has nal_unit_type equal toSTSA_N or STSA_R, each picture in the same access unit as picA in adirect or indirect reference layer of layerA shall have nal_unit_typeequal to STSA_N or STSA_R or nal_unit_type is in the range of BLA_W_LPto RSV_IRAP_VCL23, inclusive.

nuh_layer_id specifies the identifier of the layer.

When nal_unit_type is equal to AUD_NUT, the value of nuh_layer_id shallbe equal to the minimum of the nuh_layer_id values of all VCL NAL unitsin the access unit.

When nal_unit_type is equal to VPS_NUT, the value of nuh_layer_id shallbe equal to 0. Decoder shall ignore NAL units with nal_unit_type equalto VPS_NUT and nuh_layer_id greater than 0.

nuh_temporal_id_plus1_minus1 specifies a temporal identifier for the NALunit. The value of nuh_temporal_id_plus1 shall not be equal to 0.

The variable TemporalId is specified as follows:

TemporalId=nuh_temporal_id_plus1−1   (7-1)

-   -   If nal_unit_type is in the range of BLA_W_LP to RSV_IRAP_VCL23,        inclusive, i.e. the coded slice segment belongs to an IRAP        picture, TemporalId shall be equal to 0. Otherwise, when        nal_unit_type is equal to TSA_R, TSA_N, STSA_R, or STSA_N,        TemporalId shall not be equal to 0.    -   The value of TemporalId shall be the same for all VCL NAL units        of all non-IRAP coded pictures in an access unit. If in an        access unit all VCL NAL units have a nal_unit_type in the range        of BLA_W_LP to RSV_IRAP_VCL23, inclusive, i.e. the coded slice        segment belongs to an IRAP picture, the value of Temporal ID of        the access unit is 0. Otherwise the value of TemporalId of an        access unit is the value of the TemporalId of the VCL NAL units        of non-IRAP coded pictures in the access unit.

The value of TemporalId for non-VCL NAL units is constrained as follows:

-   -   If nal_unit_type is equal to VPS_NUT or SPS_NUT, TemporalId        shall be equal to 0 and the TemporalId of the access unit        containing the NAL unit shall be equal to 0.    -   Otherwise if nal_unit_type is equal to EOS_NUT or EOB_NUT,        Temporalid shall be equal to 0.    -   Otherwise, if nal_unit_type is equal to AUD_NUT or FD_NUT,        Temporalid shall be equal to the TemporalId of the access unit        containing the NAL unit.    -   Otherwise, TemporalId shall be greater than or equal to the        TemporalId of the access unit containing the NAL unit.    -   When the NAL unit is a non-VCL NAL unit, the value of TemporalId        is equal to the minimum value of the TemporalId values of all        access units to which the non-VCL NAL unit applies. When        nal_unit_type is equal to PPS_NUT, TemporalId may be greater        than or equal to the TemporalId of the containing access unit,        as all PPSs may be included in the beginning of a bitstream,        wherein the first coded picture has TemporalId equal to 0. When        nal_unit_type is equal to PREFIX_SEI_NUT or SUFFIX_SEI_NUT,        TemporalId may be greater than or equal to the TemporalId of the        containing access unit, as an SEI NAL unit may contain        information, e.g. in a buffering period SEI message or a picture        timing SEI message, that applies to a bitstream subset that        includes access units for which the Temporalid values are        greater than the TemporalId of the access unit containing the        SEI NAL unit.

In SHVC and MV-HEVC a cross_layer_irap_aligned_flag flag may be signaledin video parameter set. In particular this flag may be signaled in videoparameter set extension as shown below in Table (3).

The cross layer irap aligned flag equal to 1 specifies that TRAPpictures in the coded video sequence (CVS) are cross-layer aligned, i.e.when a picture pictureA of a layer layerA in an access unit is an IRAPpicture, each picture pictureB in the same access unit that belongs to adirect reference layer of layerA or that belongs to a layer for whichlayerA is a direct reference layer of that layer is an IRAP picture andthe VCL NAL units of pictureB have the same value of nal_unit_type asthat of pictureA.

cross_layer_irap_aligned_flag equal to 0 specifies that the aboverestriction may or may not apply.

Also in SHVC and MV-HEVC a poc_Reset_flag may be signaled in the slicesegment header.

poc_reset_flag equal to 1 specifies that the derived picture order countfor the current picture is equal to 0. poc_reset_flag equal to 0specifies that the derived picture order count for the current picturemay or may not be equal to 0. It is a requirement of bitstreamconformance that when cross layer irap aligned flag is equal to 1, thevalue of poc_reset_flag shall be equal to 0. When not present, the valueof poc_reset_flag is inferred to be equal to 0.

The restrictions related to when cross_layer_irap_aligned_flag is equalto 1 require same NAL unit type value to be used across layers. This maybe too restrictive. A modification to the restrictions whencross_layer_irap_aligned_flag is equal to 1 are described next.

In this case cross_layer_irap_aligned_flag equal to 1 specifies thatIRAP pictures in the coded video sequence (CVS) are cross-layer aligned,i.e. when a picture pictureA of a layer layerA in an access unit is anIRAP picture, each picture pictureB in the same access unit that belongsto a direct reference layer of layerA or that belongs to a layer forwhich layerA is a direct reference layer of that layer is an IRAPpicture and the VCL NAL units of pictureB have the same picture type asthat of pictureA. cross_layer_irap_aligned_flag equal to 0 specifiesthat the above restriction may or may not apply.

Thus in the above description cross_layer_irap_aligned_flag equal to 1specifies that IRAP pictures in the coded video sequence (CVS) arecross-layer aligned, i.e. when a picture pictureA of a layer layerA inan access unit is a BLA picture, each picture pictureB in the sameaccess unit that belongs to a direct reference layer of layerA or thatbelongs to a layer for which layerA is a direct reference layer of thatlayer is a BLA picture.

When a picture pictureA of a layer layerA in an access unit is a IDRpicture, each picture pictureB in the same access unit that belongs to adirect reference layer of layerA or that belongs to a layer for whichlayerA is a direct reference layer of that layer is a IDR picture.

When a picture pictureA of a layer layerA in an access unit is a CRApicture, each picture pictureB in the same access unit that belongs to adirect reference layer of layerA or that belongs to a layer for whichlayerA is a direct reference layer of that layer is a CRA picture.

The cross_layer_irap_aligned_flag equal to 0 specifies that the aboverestriction may or may not apply.

Thus as an example in this relaxed restriction pictureA could have anal_unit_type BLA_W_LP and pictureB in the same access unit could havenal_unit_type BLA_N_LP or BLA_W_RADL. Also as an example in this relaxedrestriction pictureA could have a nal_unit_type IDR_N_LP and pictureB inthe same access unit could have nal_unit_type IDR_W_RADL. This allowmore flexibility.

poc_reset_flag equal to 1 specifies that the derived picture order countfor the current picture is equal to 0. poc_reset_flag equal to 0specifies that the derived picture order count for the current picturemay or may not be equal to 0. It is a requirement of bitstreamconformance that when cross layer irap aligned flag is equal to 1, thevalue of poc_reset_flag shall be equal to 0. When not present, the valueof poc_reset_flag is inferred to be equal to 0.

In most cases, the base layer is encoded in a manner such that itresults in a HEVC compliant bitstream that is suitable to being decodedby a HEVC decoder. Similarly, the enhancement layers including SHVCand/or MV-HEVC are likewise encoded in a manner such that it results ina SHVC and/or MV-HEVC compliant bitstream suitable to be decoded by aSHVC and/or a MV-HEVC decoder. The enhancement layer(s) typically useinformation from the base layers for the decoding process. Also, if theenhancement layer(s) are removed the base layer still remains suitablefor being decoded by the HEVC decoder.

In some cases, the base layer may be encoded in a manner that results ina non-HEVC complaint bitstream that is not suitable to being decoded bya HEVC decoder. For example, the base layer may be encoded by non-HEVCcomplaint encoders, such as a MPEG-1 encoder, a MPEG-2 encoder, a AVCencoder, a VP8 encoder, a VC1 encoder etc. resulting in a correspondingbitstream. Unfortunately, the non-HEVC compliant bitstream results incomplexities of using the SHVC or MV-HEVC compliant enhancement layersbecause information expected to be provided from the base layer is notpresent.

The decoder may use an external decoder for the non-HEVC compliant baselayer that decodes the base layer and provides a series of base layerpictures, and some additional information which helps associate the baselayer decoded pictures with an access unit and provides informationabout its representation format. For example, for the current accessunit, either no information is provided (meaning no base layer pictureis used for inter-layer prediction for the current access unit,regardless whether there was a base layer picture in this access unit inthe base layer bitstream) or the following information of the base layerpicture is provided by external means: (1) the decoded sample values ofthe base layer decoded picture; (2) the representation format of thebase layer decoded picture, including the width and height in lumasamples, the colour format, the separate colour plane flag, the luma bitdepth, and the chroma bit depth; (3) whether the base layer picture isan IRAP picture or not, and if yes, the IRAP NAL unit type, which mayspecify an IDR picture, a CRA picture, or a BLA picture; and (4)optionally, whether the picture is a frame or a field, and when a field,the field parity (a top field or a bottom field). When not provided, thedecoded picture is inferred to be a frame picture

The picture order count of the base layer decoded picture is set equalto the picture order count of any enhancement layer picture, if present,in the same access unit. Note that in this case the actual picture ordercount of a base layer picture decoded by the base layer decoder in sucha scalable or multiview codec might be different than the picture ordercount value of the same picture when it is decoded by an non-HEVCdecoder. When no enhancement layer picture is present for the accessunit, the base layer decoded picture is not used and can be discarded.Also, inter-layer motion prediction from the base layer picture isdisallowed, a picture order count may be associated with the externallydecoded picture, and the picture. In this manner, the externally decodedpicture can not be used by an enhancement layer for motion prediction,but may be used for sample prediction.

The base layer is externally specified may be signaled using a flag inthe bitstream.

For example a vps_base_layer_external_flag may be defined in videoparameter set (VPS) such as shown below.

video_parameter_set_rbsp( ) { Descriptor  vps_video_parameter_set_idu(4)  vps_reserved_three_2bits u(2)  vps_max_layers_minus1 u(6) vps_max_sub_layers_minus1 u(3)  vps_temporal_id_nesting_flag u(1) vps_reserved_0xffff_16bits u(16)  profile_tier_level(vps_max_sub_layers_minus1 )  vps_sub_layer_ordering_info_present_flagu(1)  for( i = ( vps_sub_layer_ordering_info_present_flag  ? 0 :vps_max_sub_layers_minus1 );    i <= vps_max_sub_layers_minus1; i++ ) {  vps_max_dec_pic_buffering_minus1[ i ] ue(v)  vps_max_num_reorder_pics[ i ] ue(v)   vps_max_latency_increase_plus1[i ] ue(v)  }  vps_max_layer_id u(6)  vps_num_layer_sets_minus1 ue(v) for( i = 1; i <= vps_num_layer_sets_minus1; i++ )   for( j = 0; j <=vps_max_layer_id; j++ )    layer_id_included_flag[ i ][ j ] u(1) vps_timing_info_present_flag u(1)  if( vps_timing_info_present_flag ) {  vps_num_units_in_tick u(32)   vps_time_scale u(32)  vps_poc_proportional_to_timing_flag u(1)   if(vps_poc_proportional_to_timing_flag )   vps_num_ticks_poc_diff_one_minus1 ue(v)   vps_num_hrd_parametersue(v)   for( i = 0; i < vps_num_hrd_parameters; i++ ) {   hrd_layer_set_idx[ i ] ue(v)    if( i > 0 )     cprms_present_flag[ i] u(1)    hrd_parameters( cprms_present_flag[ i ],   vps_max_sub_layers_minus1 )   }  }  vps_extension_flag u(1)  if(vps_extension_flag )   while( more_rbsp_data( ) )   vps_extension_data_flag u(1)  rbsp_trailing_bits( ) }

‘vps_base_layer_external_flag’ equal to 1 may specify that the baselayer is provided by an external means not specified in the SHVC/MV-HEVCSpecification. vps_base_layer_external_flag equal to 0 may specify thatthe base layer is provided in the bitstream.

When vps_base_layer_external_flag is equal to 1, the following mayapply:

      The value of vps_sub_layer_ordering_info_present_flag shall beequal to 0.       The values of vps_max_dec_pic_buffering_minus1[ i ],vps_max_num_reorder_pics[ i ], and vps_max_latency_increase_plus1[ i ]shall all be equal to 0 for all possible values of i.       Decodersshall ignore the values of vps_sub_layer_ordering_info_present_flag,vps_max_dec_pic_buffering_minus1[ i ], vps_max_num_reorder_pics[ i ],and vps_max_latency_increase_plus1[ i ].       The value ofhrd_layer_set_idx[ i ] shall be greater than       0.

‘vps_reserved_one_bit’ shall be equal to 1 in bitstreams conforming tothis version of this Specification. The value 0 for vps_reserved_one_bitis reserved for future use by ITU-T I ISO/IEC. Decoders shall ignore thevalue of vps_reserved_one_bit.

Parameters min_spatial_segment_offset_plus1[i] [j],ctu_based_offset_enabled_flag[i] [j], andmin_horizontal_ctu_offset_plus1[i] [j] are signaled in VPS extension inJCTVC-P1008 and JCT3V-G1004. When the base layer is externally specifiedthe semantics of min_spatial_segment_offset_plus1[i] [j],min_horizontal_ctu_offset_plus1[i] [j] and related derivations utilizerefPicWidthInCtbsY[i] [j] and refPicHeightInCtbsY[i] [j] informationregarding j-th direct reference layer of i-th layer which will not beavailable when that j-th direct reference layer is non-HEVC base layerexternally specified. Without this information being available from anexternally specified base layer, it is desirable to modify the VPSextension parameters signaling so that this information is not signaled.Accordingly, as illustrated in FIG. 52 the VPS extension parametersmin_spatial_segment_offset_plus1[i] [j],ctu_based_offset_enabled_flag[i] [j], min_horizontal_ctu_offset_plus1[i][j] are preferably not signaled when base layer is externally specifiedand is one of the direct reference layers for layer i (i.e.layer_id_in_nuh[LayerIdxInVps[RefLayerId[layer_id_in_nuh[i] [j]]]]==0).

Another technique of achieve this limitation is to include a bitstreamconformance requirement that for i in the range of 1 to MaxLayerMinus1inclusive, when vps_base_layer_external_flag is equal to 1 andlayer_id_in_nuh[LayerIdxInVps[RefLayerId[layer_id_in_nuh[i] [j]]]] isequal to 0 for j in the range of 0 toNumDirectRefLayers[layer_id_in_nuh[i] ], inclusivemin_spatial_segment_offset_plus1[i] [j] is equal to value 0.

In this case additionally ctu_based_offset_enabled_flag[i] [j] isrequired to be equal to zero and min_horizontal_ctu_offset_plus1[i] [j]is required to be equal to zero.

min_spatial_segment_offset_plus1[i] [j] indicates the spatial region, ineach picture of the j-th direct reference layer of the i-th layer, thatis not used for inter-layer prediction for decoding of any picture ofthe i-th layer, by itself or together withmin_horizontal_ctu_offset_plus1[i] [j], as specified below. The value ofmin_spatial_segment_offset_plus1[i] [j] shall be in the range of 0 torefPicWidthInCtbsY[i] [j]*refPicHeightInCtbsY[i] [j], inclusive. Whennot present, the value of min_spatial_segment_offset_plus1[i] [j] isinferred to be equal to 0.

‘ctu_based_offset_enabled_flag’ [i] [j] equal to 1 specifies that thespatial region, in units of CTUs, in each picture of the j-th directreference layer of the i-th layer, that is not used for inter-layerprediction for decoding of any picture of the i-th layer is indicated bymin_spatial_segment_offset_plus1[i] [j] andmin_horizontal_ctu_offset_plus1[i] [j] together.ctu_based_offset_enabled_flag[i] [j] equal to 0 specifies that thespatial region, in units of slice segments, tiles, or CTU rows, in eachpicture of the j-th direct reference layer of the i-th layer, that isnot used for inter-layer prediction for decoding of any picture of thei-th layer is indicated by min_spatial_segment_offset_plus1[i] only.When not present, the value of ctu_based_offset_enabled_flag[i] isinferred to be equal to 0.

‘min_horizontal_ctu_offset_plus1’ [i] [j], whenctu_based_offset_enabled_flag[i] [j] is equal to 1, indicates thespatial region, in each picture of the j-th direct reference layer ofthe i-th layer, that is not used for inter-layer prediction for decodingof any picture of the i-th layer, together withmin_spatial_segment_offset_plus1[i] [j], as specified below. The valueof min_horizontal_ctu_offset_plus1[i] [j] shall be in the range of 0 torefPicWidthInCtbsY[i] [j], inclusive.

When ctu_based_offset_enabled_flag[i] [j] is equal to 1, the variableminHorizontalCtbOffset[i] [j] is derived as follows:minHorizontalCtbOffset[i] [j]=(min_horizontal_ctu_offset_plus1[i][j]>0)?(min_horizontal_ctu_offset_plus1[i] [j]−1):(refPicWidthInCtbsY[i] [j]1)

The variables curPicWidthInSamples_(L)[i], curPicHeightInSamples_(L)[i],curCtbLog2SizeY[i], curPicWidthInCtbsY[i], and curPicHeightInCtbsY[i]are set equal to PicWidthInSamples_(L), PicHeightInSamples_(L),CtbLog2SizeY, PicWidthInCtbsY, and PicHeightInCtbsY, respectively, ofthe i-th layer.

The variables refPicWidthInSamples_(L)[i] [j],refPicHeightInSamples_(L)[i] [j], refCtbLog2SizeY[i] [j],refPicWidthInCtbsY[i] [j], and refPicHeightInCtbsY[i] [j] are set equalto PicWidthInSamples_(L), PicHeightInSamples_(L), CtbLog2SizeY,PicWidthInCtbsY, and PicHeightInCtbsY, respectively, of the j-th directreference layer of the i-th layer.

The variables curScaledRefLayerLeftOffset[i] [j],curScaledRefLayerTopOffset[i] [j], curScaledRefLayerRightOffset[i] [j]and curScaledRefLayerBottomOffset[i] [j] are set equal toscaled_ref_layer_left_offset[j]<<1, scaled ref layer top offset[j]<<1,scaled_ref_layer_right_offset[j]<<1, scaled_ref_layer_bottom_offset[j]<<1, respectively, of the j-th direct reference layer of the i-thlayer.

The variable colCtbAddr[i] [j] that denotes the raster scan address ofthe collocated CTU, in a picture in the j-th direct reference layer ofthe i-th layer, of the CTU with raster scan address equal to ctbAddr ina picture of the i-th layer is derived as follows:

   The variables ( xP, yP ) specifying the location of the top-left lumasample of the CTU with raster scan address equal to ctbAddr relative totop-left luma luma sample in a picture of the i-th layer are derived asfollows:    xP = ( ctbAddr % curPicWidthInCtbsY[ i ] ) <<curCtbLog2SizeY    yP = ( ctbAddr / curPicWidthInCtbsY[ i ] ) <<curCtbLog2SizeY    The variables scaleFactorX[ i ][ j ] andscaleFactorY[ i ][ j ] are derived as follows:   curScaledRefLayerPicWidthInSamples_(L)[ i ][ j ] =curPicWidthInSamples_(L)[ i ] −    curScaledRefLayerLeftOffset[ i ][ j ]− curScaledRefLayerRightOffset[ i ][ j ]   curScaledRefLayerPicHeightInSamples_(L)[ i ][ j ] =curPicHeightInSamples_(L)[ i ] −    curScaledRefLayerTopOffset[ i ][ j ]− curScaledRefLayerBottomOffset[ i ][ j ]    scaleFactorX[ i ][ j ] = (( refPicWidthInSamples_(L) [ i ][ j ] << 16 ) + (curScaledRefLayerPicWidthInSamples_(L) [ i ][ j ]>> 1 ))/curScaledRefLayerPicWidthInSamples_(L) [ i ][ j ]    scaleFactorY[ i][ j ] = ( ( refPicHeightInSamples_(L) [ i ][ j ] << 16 ) + (curScaledRefLayerPicHeightInSamples_(L) >> 1 ) ) /curScaledRefLayerPicHeightInSamples_(L) [ i ][ j ]    The variables (xCol[ i ][ j ], yCol xCol[ i ][ j ]) specifying the collocated lumasample location in a picture in the j-th direct reference layer of theluma sample location ( xP, yP ) in the i-th layer are derived asfollows:    xCol [ i ][ j ] = Clip3( 0, ( refPicWidthInSamples_(L)[ i ][j ]− 1 ), ( ( xP − curScaledRefLayerLeftOffset[ i ][ j ]) *scaleFactorX[ i ][ j ] + ( 1 << 15 ) ) >> 16))    yCol [ i ][ j ] =Clip3( 0 , ( refPicHeightInSamples_(L)[ i ][ j ]− 1 ), ( ( yP −curScaledRefLayerTopOffset[ i ][ j ]) * scaleFactorY[ i ][ j ] + ( 1 <<15 ) ) >> 16))    The variable colCtbAddr[ i ][ j ] is derived asfollows:    xColCtb[ i ][ j ] = xCol[ i ][ j ] >> refCtbLog2SizeY[ i ][j ]    yColCtb[ i ][ j ] = yCol[ i ][ j ] >> refCtbLog2SizeY[ i ][ j ]   colCtbAddr[ i ][ j ] = xColCtb[ i ][ j ] + ( yColCtb[ i ][ j ] *refPicWidthInCtbsY[ i ][ j ] )

When min_spatial_segment_offset_plus1[i] [j] is greater than 0, it is arequirement of bitstream conformance that the following shall apply:

-   -   If ctu_based_offset_enabled_flag[i] [j] is equal to 0, exactly        one of the following applies:        -   In each PPS referred to by a picture in the j-th direct            reference layer of the i-th layer, tiles_enabled_flag is            equal to 0 and entropy_coding_sync_enabled_flag is equal to            0, and the following applies:            -   Let slice segment A be any slice segment of a picture of                the i-th layer and ctbAddr be the raster scan address of                the last CTU in slice segment A. Let slice segment B be                the slice segment that belongs to the same access unit                as slice segment A, belongs to the j-th direct reference                layer of the i-th layer, and contains the CTU with                raster scan address colCtbAddr[i] [j]. Let slice segment                C be the slice segment that is in the same picture as                slice segment B and follows slice segment B in decoding                order, and between slice segment B and that slice                segment there are min_spatial_segment_offset_plus1[i−1                slice segments in decoding order. When slice segment C                is present, the syntax elements of slice segment A are                constrained such that no sample or syntax elements                values in slice segment C or any slice segment of the                same picture following C in decoding order are used for                inter-layer prediction in the decoding process of any                samples within slice segment A.    -   In each PPS referred to by a picture in the j-th direct        reference layer of the i-th layer, tiles_enabled_flag is equal        to 1 and entropy_coding_sync_enabled_flag is equal to 0, and the        following applies:        -   Let tile A be any tile in any picture picA of the i-th layer            and ctbAddr be the raster scan address of the last CTU in            tile A. Let tile B be the tile that is in the picture picB            belonging to the same access unit as picA and belonging to            the j-th direct reference layer of the i-th layer and that            contains the CTU with raster scan address colCtbAddr[i] [j].            Let tile C be the tile that is also in picB and follows tile            B in decoding order, and between tile B and that tile there            are min_spatial_segment_offset_plus1[i−1 tiles in decoding            order. When slice segment C is present, the syntax elements            of tile A are constrained such that no sample or syntax            elements values in tile C or any tile of the same picture            following C in decoding order are used for inter-layer            prediction in the decoding process of any samples within            tile A.        -   In each PPS referred to by a picture in the j-th direct            reference layer of the i-th layer, tiles_enabled_flag is            equal to 0 and entropy_coding_sync_enabled_flag is equal to            1, and the following applies:            -   Let CTU row A be any CTU row in any picture picA of the                i-th layer and ctbAddr be the raster scan address of the                last CTU in CTU row A. Let CTU row B be the CTU row that                is in the picture picB belonging to the same access unit                as picA and belonging to the j-th direct reference layer                of the i-th layer and that contains the CTU with raster                scan address colCtbAddr[i] [j]. Let CTU row C be the CTU                row that is also in picB and follows CTU row B in                decoding order, and between CTU row B and that CTU row                there are min_spatial_segment_offset_plus1[i−1 CTU rows                in decoding order. When CTU row C is present, the syntax                elements of CTU row A are constrained such that no                sample or syntax elements values in CTU row C or row of                the same picture following C are used for inter-layer                prediction in the decoding process of any samples within                CTU row A.

   Otherwise (ctu_based_offset_enabled_flag[ i ][ j ] is equal to 1),the following applies:    The variable refCtbAddr[ i ][ j ] is derivedas follows:       xOffset[ i ][ j ] =    ( ( xColCtb[ i ][ j ] +minHorizontalCtbOffset[ i ][ j ] ) > ( refPicWidthInCtbsY[ i ][ j ] −   1 ) ) ?       ( refPicWidthInCtbsY[ i ][ j ] − 1 −xColCtb[ i ][ j ] ):    ( minHorizontalCtbOffset[ i ][ j ] )       yOffset[ i ][ j ] = (min_spatial_segment_offset_plus1[ i ][ j ] −    1 ) *refPicWidthInCtbsY[ i ][ j ]       refCtbAddr[ i ][ j ] = colCtbAddr[ i][ j ] + xOffset[ i ][ j ] + yOffset[ i ][ j ]

-   -   -   Let CTU A be any CTU in any picture picA of the i-th layer,            and ctbAddr be the raster scan address ctbAddr of CTU A. Let            CTU B be a CTU that is in the picture belonging to the same            access unit as picA and belonging to the j-th direct            reference layer of the i-th layer and that has raster scan            address greater than refCtbAddr[i] [j]. When CTU B is            present, the syntax elements of CTU A are constrained such            that no sample or syntax elements values in CTU B are used            for inter-layer prediction in the decoding process of any            samples within CTU A.

When the base layer is externally specified the information regardingtiling structure, if any for it, is unknown. Thus alignment of the tilesbetween a i-th layer and j-th direct reference layer of i-th layer whenthat j-th direct reference layer is externally specified base layer isnot known and is not signaled. Without this information being availablewith an externally specified base layer, it is desirable to modify theVPS extension parameters signaling so that this information is notsignaled. Accordingly, as illustrated in FIG. 53 the VPS extensionparameter tile_boundaries_aligned_flag[i] [j], is preferably notsignaled when base layer is externally specified and is one of thedirect reference layers for layer i (i.e.layer_id_in_nuh[LayerIdxInVps[RefLayerId[layer_id_in_nuh[i] [j]]]]==0).

Another technique of achieve this limitation is to include a bitstreamconformance requirement that for i in the range of 1 to MaxLayerMinus1inclusive, when vps_base_layer_external_flag equal to 1 andlayer_id_in_nuh[LayerIdxInVps[RefLayerId[layer_id_in_nuh[i] [j]]]] isequal to 0 for j in the range of 0 toNumDirectRefLayers[layer_id_in_nuh[i] ], inclusivetile_boundaries_aligned_flag[i] [j] is equal to value 0.

‘tile_boundaries_aligned_flag’ [i] [j] equal to 1 indicates that, whenany two samples of one picture of the i-th layer specified by the VPSbelong to one tile, the two collocated samples, when both present in thepicture of the j-th direct reference layer of the i-th layer, belong toone tile, and when any two samples of one picture of the i-th layerbelong to different tiles, the two collocated samples, when both presentin the picture of the j-th direct reference layer of the i-th layerbelong to different tiles. tile boundaries aligned flag equal to 0indicates that such a restriction may or may not apply. When notpresent, the value of tile boundaries aligned flag[i] [j] is inferred tobe equal to 0.

Additionally in FIG. 53, the tile_boundaires_aligned_flag[i] [j] issignaled for the first enhancement layer.

For layer sets, the externally specified base layer does not include abitrate or picture rate information, and accordingly, there suchinformation is preferably not signaled as part of the layer sets. Thefirst layer set has only the base layer in it, and accordingly, if thebase layer is externally specified then it is not desirable to signalthat layer set (and sub-layer set). Referring to FIG. 54, for layer setsit is desirable to start the indexing at i=1 for externally signaledbase layers, and i=0 for HEVC signaled base layer.

In the case of externally specified base layer, a variable BlIrapPicFlag(base layer irap picture flag) is provided by external means and ifBlIrapPicFlag is equal to 1 (i.e. decoded picture is IRAP picture) valueof nal_unit_Type is provided by external means. Thus the value ofnal_unit_type fot the base layer is only provided if it is a IRAPpicture. For other picture types the nal_unit_Type of externallyprovided base layer picture is not provided. Thus TSA_N or TSA_Rnal_unit_type is not signaled for an externally specified base layer.Thus the cross-layer alignment when such a externally specified baselayer is direct or indirect reference layer of another layer may berelaxed.

This relaxation with respect to TSA_N or TSA_R may be achieved by whenone picture picA of a layer layerA has nal_unit_type equal to TSA_N orTSA_R, each picture in the same access unit as picA in a direct orindirect reference layer of layerA with the exception of layer withnuh_layer_id equal to 0 when vps_base_layer_external_flag is equal to 1shall have nal_unit_type equal to TSA_N or TSA_R. Accordingly,externally specified pictures can have a NAL unit type of IRAP definedif an IRAP picture but can't specify if a TSA_N or TSA_R because theexternally specified picutres may not have the concept of a TSA picture,so relaxing the restriction accommodates the use of TSA_N and/or TSA_Rin the enhancement layers.

In another embodiment the relaxation with respect to TSA_N or TSA_R maybe achieved by when one picture picA of a layer layerA has nal_unit_typeequal to TSA_N or TSA_R, each coded picture in the same access unit aspicA in a direct or indirect reference layer of layerA shall havenal_unit_type equal to TSA_N or TSA_R. By specifying coded picture inthis restriction the externally specified base layer for which onlydecoded picture is provided by external means is excluded from thisrestriction when externally specified base layer is a direct referencelayer.

In the case of externally specified base layer a variable BlIrapPicFlagis provided by external means and if BlIrapPicFlag is equal to 1 (i.e.decoded picture is IRAP picture) value of nal_unit_type is provided byexternal means. Thus the value of nal_unit_type fot the base layer isonly provided if it is a IRAP picture. For other picture types thenal_unit_Type of externally provided base layer picture is not provided.Thus STSA_N or STSA_R nal_unit_type is not signaled for an externallyspecified base layer. Thus the cross-layer alignment when such aexternally specified base layer is direct or indirect reference layer ofanother layer may be relaxed.

This relaxation with respect to STSA_N or STSA_R may be achieved by whenone picture picA of a layer layerA has nal_unit_type equal to STSA_N orSTSA_R, each picture in the same access unit as picA in a direct orindirect reference layer of layerA with the exception of layer withnuh_layer_id equal to 0 when vps_base_layer_external_flag is equal to 1shall have nal_unit_type equal to STSA_N or STSA_R. Accordingly,externally specified pictures can have a NAL unit type of IRAP definedif an IRAP picture but can't specify if a STSA_N or STSA_R because theexternally specified picutres may not have the concept of a STSApicture, so relaxing the restriction accommodates the use of STSA_Nand/or STSA_R in the enhancement layers.

In another embodiment the relaxation with respect to STSA_N or STSA_Rmay be achieved by when one picture picA of a layer layerA hasnal_unit_type equal to STSA_N or STSA_R, each coded picture in the sameaccess unit as picA in a direct or indirect reference layer of layerAshall have nal_unit_type equal to STSA_N or STSA_R. By specifying codedpicture in this restriction the externally specified base layer forwhich only decoded picture is provided by external means is excludedfrom this restriction when externally specified base layer is a directreference layer.

For any particular access unit (see FIG. 17 and FIG. 29), HEVCcompliance has a requirement that the TemporalId is the same for thebase layer and the enhancement layers. With the pictures for theexternally specified base layers not having a TemporalId, it isdesirable to assign TemporalId for the picture of the externallyspecified base layer.

This requirement with respect to TemporalId may be expressed as thevalue of TemporalId shall be the same for all VCL NAL units of an accessunit. When vps_base_layer_external_flag is equal to 1 the value ofTemporalId of a picture with nuh_layer_id equal to 0 is inferred.Otherwise the value of TemporalId of a coded picture or an access unitis the value of the TemporalId of the VCL NAL units of the coded pictureor the access unit. The value of TemporalId of a sub-layerrepresentation is the greatest value of TemporalId of all VCL NAL unitsin the sub-layer representation. The decoding process may implement thefollowing, if the access unit has at least one picture with nuh_layer_idgreater than 0, TemporalId of the decoded picture for the externallyspecified ase layer with nuh_layer_id equal to 0 is set equal to theTemporalId of any picture with nuh_layer_id greater than 0 in the accessunit.

Another technique to achieve a similar TemporalId expression is thevalue of TemporalId shall be the same for all VCL NAL units of an accessunit when vps_base_layer_external_flag is equal to 0. The value ofTemporalId shall be the same for all VCL NAL units with nuh_layer_id>0of an access unit when vps_base_layer_external_flag is equal to 1. Whenvps_base_layer_external_flag is equal to 1 the value of TemporalId of apicture with nuh_layer_id equal to 0 is inferred. Whenvps_base_layer_external_flag is equal to 0 the value of TemporalId of acoded picture or an access unit is the value of the TemporalId of theVCL NAL units of the coded picture or the access unit. Whenvps_base_layer_external_flag is equal to 1 the value of TemporalId of acoded picture with nuh_layer_id>0 or an access unit is the value of theTemporalId of the VCL NAL units of the coded picture withnuh_layer_id>0. The value of TemporalId of a sub-layer representation isthe greatest value of TemporalId of all VCL NAL units in the sub-layerrepresentation. The decoding process may implement the following, IfBlIrapPicFlag is equal to 1 the TemporalId of the decoded picture withnuh_layer_id equal to 0 is set equal to 0. Otherwise (if BlIrapPicFlagis equal to 0) if the access unit has at least one picture withnuh_layer_id greater than 0, TemporalId of the decoded picture withnuh_layer_id equal to 0 is set equal to the TemporalId of any picturewith nuh_layer_id greater than 0 in the access unit.

The semantics for the TemporalId for the NAL unit header semantics maybe as follows.

nuh_temporal_id_plus1_minus1 specifies a temporal identifier for the NALunit. The value of nuh_temporal_id_plus1 shall not be equal to 0. Thevariable TemporalId is specified as follows:

TemporalId=nuh_temporal_id_plus1−1

If nal_unit_type is in the range of BLA_W_LP to RSV_IRAP_VCL23,inclusive, i.e. the coded slice segment belongs to an IRAP picture,TemporalId shall be equal to 0. Otherwise, when nal_unit_type is equalto TSA_R, TSA_N, STSA_R, or STSA_N, TemporalId shall not be equal to 0.

] In one variation, the value of TemporalId shall be the same for allVCL NAL units of an access unit. When vps_base_layer_external_flag isequal to 1 the value of TemporalId of a picture with nuh_layer_id equalto 0 is inferred as described in section F 8.1—General decoding process.Otherwise the value of TemporalId of a coded picture or an access unitis the value of the TemporalId of the VCL NAL units of the coded pictureor the access unit. The value of TemporalId of a sub-layerrepresentation is the greatest value of TemporalId of all VCL NAL unitsin the sub-layer representation.

In another variation, the value of TemporalId shall be the same for allVCL NAL units of an access unit when vps_base_layer_external_flag isequal to 0. The value of TemporalId shall be the same for all VCL NALunits with nuh_layer_id>0 of an access unit whenvps_base_layer_external_flag is equal to 1. Whenvps_base_layer_external_flag is equal to 1 the value of TemporalId of apicture with nuh_layer_id equal to 0 is inferred as described in sectionF 8.1—General decoding process. When vps_base_layer_external_flag isequal to 0 the value of TemporalId of a coded picture or an access unitis the value of the TemporalId of the VCL NAL units of the coded pictureor the access unit. When vps_base_layer_external_flag is equal to 1 thevalue of TemporalId of a coded picture with nuh_layer_id>0 or an accessunit is the value of the TemporalId of the VCL NAL units of the codedpicture with nuh_layer_id>0. The value of TemporalId of a sub-layerrepresentation is the greatest value of TemporalId of all VCL NAL unitsin the sub-layer representation.

The value of TemporalId for non-VCL NAL units is constrained as follows:

-   -   If nal_unit_type is equal to VPS_NUT or SPS_NUT, TemporalId        shall be equal to 0 and the TemporalId of the access unit        containing the NAL unit shall be equal to 0.    -   Otherwise if nal_unit_type is equal to EOS_NUT or EOB_NUT,        TemporalId shall be equal to 0.    -   Otherwise, if nal_unit_type is equal to AUD_NUT or FD_NUT,        TemporalId shall be equal to the TemporalId of the access unit        containing the NAL unit.    -   Otherwise, TemporalId shall be greater than or equal to the        TemporalId of the access unit containing the NAL unit.

It is noted that when the NAL unit is a non-VCL NAL unit, the value ofTemporalId is equal to the minimum value of the TemporalId values of allaccess units to which the non-VCL NAL unit applies. When nal_unit_typeis equal to PPS_NUT, TemporalId may be greater than or equal to theTemporalId of the containing access unit, as all PPSs may be included inthe beginning of a bitstream, wherein the first coded picture hasTemporalId equal to 0. When nal_unit_type is equal to PREFIX_SEI_NUT orSUFFIX_SEI_NUT, TemporalId may be greater than or equal to theTemporalId of the containing access unit, as an SEI NAL unit may containinformation, e.g. in a buffering period SEI message or a picture timingSEI message, that applies to a bitstream subset that includes accessunits for which the TemporalId values are greater than the TemporalId ofthe access unit containing the SEI NAL unit.

The general decoding process (Section F.8.1) may be as follows, whichincludes accommodations for the TemporalId and the externally referencedbase layer:

-   -   When vps_base_layer_external_flag is equal to 1, the following        applies:        -   There is no coded picture with nuh_layer_id equal to 0 in            the bitstream.        -   The size of the sub-DPB for the layer with nuh_layer_id            equal to 0 is set equal to 1.        -   The values of pic_width_in_luma_samples,            pic_height_in_luma_samples, chroma_format_idc,            separate_colour_plane_flag, bit_depth_luma_minus8, and bit            depth_chroma_minus8 for decoded pictures with nuh_layer_id            equal to 0 are set equal to the values of            pic_width_vps_in_luma_samples,            pic_height_vps_in_luma_samples, chroma_format_vps_idc,            separate_colour_plane_vps_flag, bit_depth_vps_luma_minus8,            and bit_depth_vps_chroma_minus8, respectively, of the            vps_rep_format_idx[0]-th rep_format( ) syntax structure in            the active VPS.        -   In addition to a list of decoded pictures, this process also            outputs a flag BaseLayerOutputFlag, and, when            BaseLayerOutputFlag is equal to 0 and            AltOptLayerFlag[TargetOptLayerSetIdx] is equal to 1, a flag            BaseLayerPicOutputFlag for each access unit. The            BaseLayerOutputFlag and, when present,            BaseLayerPicOutputFlag for each access unit, are to be sent            by an external means to the base layer decoder for            controlling the output of base layer decoded pictures. The            following applies:            -   BaseLayerOutputFlag is derived as follows:        -   BaseLayerOutputFlag=(TargetOptLayerIdList[0]==0).        -   BaseLayerOutputFlag equal to 1 specifies that the base layer            is a target output layer. BaseLayerOutputFlag equal to 0            specifies that the base layer is a not target output layer.            -   When BaseLayerOutputFlag is equal to 0 and                AltOptLayerFlag[TargetOptLayerSetIdx] is equal to 1, for                each access unit, BaseLayerPicOutputFlag is derived as                follows: if (the base layer is a direct or indirect                reference layer of the target output layer, the access                unit does not contain a picture at the target output                layer and does not contain a picture at any other direct                or indirect reference layer of the target output layer)                -   BaseLayerPicOutputFlag=1                -    else                -   BaseLayerPicOutputFlag=0            -   BaseLayerPicOutputFlag equal to 1 for an access unit                specifies that the base layer picture of the access unit                is output. BaseLayerPicOutputFlag equal to 0 for an                access unit specifies that the base layer picture of the                access unit is not output.        -   For each access unit, a decoded picture with nuh_layer_id            equal to 0 may be provided by external means. When not            provided, no picture with nuh_layer_id equal to 0 is used            for inter-layer prediction for the current access unit. When            provided, the following applies:            -   The following information of the picture with                nuh_layer_id equal to 0 for the access unit is provided                by external means:                -   The decoded sample values (1 sample array SL if                    chroma_format_idc is equal to 0 or 3 sample arrays                    SL, SCb, and SCr otherwise)                -   The value of the variable BlIrapPicFlag, and when                    BlIrapPicFlag is equal to 1, the value of                    nal_unit_type of the decoded picture                -    BlIrapPicFlag equal to 1 specifies that the decoded                    picture is an IRAP picture. BlIrapPicFlag equal to 0                    specifies that the decoded picture is a non-IRAP                    picture.                -     The provided value of nal_unit_type of the decoded                    picture shall be equal to IDR_W_RADL, CRA_NUT, or                    BLA_W_LP.                -      nal_unit_type equal to IDR_W_RADL specifies that                    the decoded picture is an IDR picture.                -      nal_unit_type equal to CRA_NUT specifies that the                    decoded picture is a CRA picture.                -      nal_unit_type equal to BLA_W_LP specifies that                    the decoded picture is a BLA picture.            -   The following applies for the decoded picture with                nuh_layer_id equal to 0 for the access unit:                -   The decoded picture with nuh_layer_id equal to 0 is                    stored in the sub-DPB for the layer with                    nuh_layer_id equal to 0 and is marked as “used for                    long-term reference”.                -   If the access unit has at least one picture with                    nuh_layer_id greater than 0, the PicOrderCntVal of                    the decoded picture with nuh_layer_id equal to 0 is                    set equal to the PicOrderCntVal of any picture with                    nuh_layer_id greater than 0 in the access unit.                    Otherwise, the decoded picture with nuh_layer_id                    equal to 0 is discarded and the sub-DPB for the                    layer with nuh_layer_id equal to 0 is set to be                    empty.            -   In one embodiment, if the access unit has at least one                picture with nuh_layer_id greater than 0, TemporalId of                the decoded picture with nuh_layer_id equal to 0 is set                equal to the TemporalId of any picture with nuh_layer_id                greater than 0 in the access unit.

In another embodiment, if BlIrapPicFlag is equal to 1 the TemporalId ofthe decoded picture with nuh_layer_id equal to 0 is set equal to 0.Otherwise (if BlIrapPicFlag is equal to 0) if the access unit has atleast one picture with nuh_layer_id greater than 0, TemporalId of thedecoded picture with nuh_layer_id equal to 0 is set equal to theTemporalId of any picture with nuh_layer_id greater than 0 in the accessunit.

-   -   -   When the access unit has at least one picture with            nuh_layer_id greater than 0, after all pictures in the            access unit are decoded, the sub-DPB for the layer with            nuh_layer_id equal to 0 is set to be empty.        -   Thus in the above decoding process in one of the embodiments            the TemporalId of all coded pictures belonging to one access            unit may not be same. Thus the TemporalId of all VCL NAL            units of coded pictures belonging to one access unit may not            be same. In particular in case the base layer is externally            specified the TemporalId of all coded pictures belonging to            one access unit may not be same. Thus in case the base layer            is externally specified the TemporalId of all VCL NAL units            of coded pictures belonging to one access unit may not be            same. Thus the constraint that all the VCL NAL units or all            coded pictures belonging to the same access unit must have            same TemporalId value is relaxed.

Another approach to handle the temporal identifier (TemporalId) for theexternally specified base layer pictures is now defined. Instead ofdefining a derivation or inference of TemporalId value for externallyspecified base layer pictures, modifications are made in semantics ofvarious syntax elements. Also additional bitstream conformanceconstraints are defined when the base layer is externally specified.

An exemplary vps extension syntax is shown below.

vps_extension( ) { Descriptor  avc_base_layer_flag u(1)  splitting_flagu(1)  for( i = 0, NumScalabilityTypes = 0; i < 16; i++ ) {  scalability_mask_flag[ i ] u(1)   NumScalabilityTypes +=scalability_mask_flag[ i ]  }  for( j = 0; j < ( NumScalabilityTypes −splitting_flag ); j++ )   dimension_id_len_minus1[ j ] u(3) vps_nuh_layer_id_present_flag u(1)  for( i = 1; i <= MaxLayersMinus1;i++ ) {   if( vps_nuh_layer_id_present_flag )    layer_id_in_nuh[ i ]u(6)   if( !splitting_flag )    for( j = 0; j < NumScalabilityTypes; j++)     dimension_id[ i ][ j ] u(v)  }  view_id_len u(4)  if(view_id_len > 0)   for( i = 0; i < NumViews; i++ )    view_id_val[ i ]u(v)  for( i = 1; i <= MaxLayersMinus1; i++ )   for( j = 0; j < i; j++ )   direct_dependency_flag[ i ][ j ] u(1) vps_sub_layers_max_minus1_present_flag u(1)   if(vps_sub_layers_max_minus1_present_flag )    for( i = 0; i <=MaxLayersMinus1; i++ )     sub_layers_vps_max_minus1[ i ] u(3) max_tid_ref_present_flag u(1)  if( max_tid_ref_present_flag )   for( i= 0; i < MaxLayersMinus1; i++ )    for( j = i + 1; j <= MaxLayersMinus1;j++ )     if( direct_dependency_flag[ j ][ i ] )     max_tid_il_ref_pics_plus1[ i ][ j ] u(3) all_ref_layers_active_flag u(1)  vps_num_profile_tier_level_minus1ue(v)  for( ptlIdx = 1; ptlIdx <= vps_num_profile_tier_level_minus1;ptlIdx ++ ) {   vps_profile_present_flag[ ptlIdx ] u(1)  profile_tier_level( vps_profile_present_flag[ ptlIdx ],vps_max_sub_layers_minus1 )  }  num_add_output_layer_sets ue(v) NumOutputLayerSets = num_add_output_layer_sets +vps_num_layer_sets_minus1 + 1  if( NumOutputLayerSets > 1 )  default_target_output_layer_idc u(2)  for( i = 1; i <NumOutputLayerSets; i++ ) {   if( i > vps_num_layer_sets_minus1 )   output_layer_set_idx_minus1[ i ] u(v)   if( i >vps_num_layer_sets_minus1 || default_target_output_layer_idc = = 2 )   for( j = 0; j < NumLayersInIdList[ LayerSetIdxForOutputLayerSet[ i ]]; j++)     output_layer_flag[ i ][ j ] u(1)   profile_level_tier_idx[ i] u(v)   if( NumOutputLayersInOutputLayerSet[ i ] = = 1    &&NumDirectRefLayers[ OlsHighestOutputLayerId[ i ] ] > 0 )   alt_output_layer_flag[ i ] u(1)  }  rep_format_idx_present_flag u(1) if( rep_format_idx_present_flag )   vps_num_rep_formats_minus1 ue(v) for( i = 0; i <= vps_num_rep_formats_minus1; i++ )   rep_format( )  if(rep_format_idx_present_flag )   for( i = 1; i <= MaxLayersMinus1; i++ )   if( vps_num_rep_formats_minus1 > 0 )     vps_rep_format_idx[ i ] u(v) max_one_active_ref_layer_flag u(1)  vps_poc_lsb_aligned_flag u(1)  for(i = 1; i <= MaxLayersMinus1; i++ )   if( NumDirectRefLayers[layer_id_in_nuh[ i ] ] = = 0 )    poc_lsb_not_present_flag[ i ] u(1) cross_layer_phase_alignment_flag u(1)  dpb_size( ) direct_dep_type_len_minus2 ue(v)  default_direct_dependency_flag u(1) if( default_direct_dependency_flag )   default_direct_dependency_typeu(v)  else {   for( i = 1; i <= MaxLayersMinus1; i++ )    for( j = 0; j< i; j++ )     if( direct_dependency_flag[ i ][ j ] )     direct_dependency_type[ i ][ j ] u(v)  } vps_non_vui_extension_length ue(v)  for( i = 1; i <=vps_non_vui_extension_length; i++ )   vps_non_vui_extension_data_byteu(8)  vps_vui_present_flag  if( vps_vui_present_flag ) {   while(!byte_aligned( ) )    vps_vui_alignment_bit_equal_to_one u(1)   vps_vui()  } }

Following modifications are defined to handle the temporal identifierfor externally specified base layer.

-   -   Semantics of max_tid_il_ref_pics_plus1[i] [j] are modified when        layer_id_in_nuh[i] is equal to 0 and        vps_external_base_layer_flag is equal to 1.    -   Semantics of all_ref_layers_active_flag is modified.    -   Semantics of num_inter_layer_ref_pics_minus1 is modified with        respect to the derivation of refLayerPicIdc when a direct        reference layer is externally specified base layer.    -   A condition is added regarding bitstream conformance for each        value of i in the range of 0 to NumActiveRefLayerPics−1,        inclusive.    -   A modification is applied to marking process for sub-layer        non-reference pictures not needed for inter-layer prediction.

In JCTVC-P1008 and JCT3V-G1004, both of which are incorporated byreference herein in their entirety, max_tid_il_ref_pics_plus1[i] [j]values are signaled in the video parameter set (VPS) extension.max_tid_il_ref_pics_plus1[i] [j] equal to 0 specifies that within theCVS non-TRAP pictures with nuh_layer_id equal to layer_id_in_nuh[i] arenot used as reference for inter-layer prediction for pictures withnuh_layer_id equal to layer id in nuh[j]. max_tid_il_ref_pics_plus1[i][j] greater than 0 specifies that within the CVS pictures withnuh_layer_id equal to layer id in nuh[i] and TemporalId greater than maxtid il ref pics plus1[i] [j]−1 are not used as reference for inter-layerprediction for pictures with nuh_layer_id equal to layer_id_in_nuh[j].

HEVC, SHVC, and MV-HEVC incorporate a multi-loop decoding technique. Forexample, a bitstream may include layers 0, 1, and 2. If it is desirableto decode layer 2, then the decoder needs to decode layer 1 and layer 0if the layer 0 and layer 1 are used as a reference layers for layer 2.This is a computationally burdensome task to decode layers 0 and 1 ifonly layer 2 is desirable to be decoded and displayed or played back. Insome case the layer 2 may be termed a target layer. One technique toreduce the complexity of a multi-loop decoder, is to signal value formax_tid_il_ref_pics_plus1[i] [j] which describes inter-layer predictionrestriction. However the max_tid_il_ref_pics_plus1[i] [j] semantics needto be modified when an externally specified base layer is involved.

Semantics of max_tid_il_ref_pics_plus1[i] [j] are modified when layer idin nuh[ i] is equal to 0 and vps_external_base_layer_flag is equal to 1.

When base layer is externally specified (i.e.vps_base_layer_external_flag is equal to 1) the semantics ofmax_tid_il_ref_pics_plus1[i] [j] are modified to handle the aspect thatTemporalId value of the externally specified base layer pictures (withlayer id in nuh[i] is equal to 0) is unknown. Thus in this case the useof these externally specified base layer pictures as inter-layerreference pictures for another layer (e.g. for layer withlayer_id_in_nuh[j]) is based on the values signaled in the slice segmentheader of that layer.

‘max_tid_ref_present_flag’ equal to 1 may specify that the syntaxelement max_tid_il_ref_pics_plus1[i] [j] is present.max_tid_ref_present_flag equal to 0 may specify that the syntax elementmax_tid_il_ref_pics_plus1[i] [j] is not present.

‘max_tid_il_ref_pics_plus1’ [i] [j] equal to 0 may specify that withinthe CVS non-IRAP pictures with nuh_layer_id equal to layer_id_in_nuh[i]are not used as reference for inter-layer prediction for pictures withnuh_layer_id equal to layer_id_in_nuh[j]. max_tid_il_ref_pics_plus1 [i][j] greater than 0 specifies that:

-   -   When layer_id_in_nuh[i] is equal to 0 and        vps_external_base_layer_flag is equal to 1, within the CVS        pictures with nuh_layer_id equal to layer_id_in_nuh[i] may or        may not be used as reference pictures for inter-layer prediction        as specified by the values of inter_layer_pred_enabled_flag,        num_inter_layer_ref_pics_minus1_and inter_layer_pred_idc[k]        values in the slice segment header of pictures with nuh_layer_id        equal to layer_id_in_nuh[j].    -   Otherwise within the CVS pictures with nuh_layer_id equal to        layer_id_in_nuh[i] and TemporalId greater than        max_tid_il_ref_pics_plus1[i] [j]−1 are not used as reference for        inter-layer prediction for pictures with nuh_layer_id equal to        layer_id_in_nuh[j].

When not present, max_tid_il_ref_pics_plus1[i] [j] may be inferred to beequal to 7.

In another embodiment ‘max_tid_il_ref_pics_plus1’ [i] [j] equal to 0 mayspecify that:

-   -   when layer_id_in_nuh[i] is equal to 0 and        vps_external_base_layer_flag is equal to 1, non-IRAP pictures        with nuh_layer_id equal to layer_id_in_nuh[i] may or may not be        used as reference for inter-layer prediction for pictures with        nuh_layer_id equal to layer_id_in_nuh[j].    -   Otherwise within the CVS non-IRAP pictures with nuh_layer_id        equal to layer_id_in_nuh[i] are not used as reference for        inter-layer prediction for pictures with nuh_layer_id equal to        layer_id_in_nuh[j].

max_tid_il_ref_pics_plus1[i] [j] greater than 0 specifies that:

-   -   When layer_id_in_nuh[i] is equal to 0 and        vps_external_base_layer_flag is equal to 1, within the CVS        pictures with nuh_layer_id equal to layer_id_in_nuh[i] may or        may not be used as reference pictures for inter-layer prediction        as specified by the values of inter_layer_pred_enabled_flag,        num_inter_layer_ref_pics_minus1_and inter_layer_pred_idc[k ]        values in the slice segment header of pictures with nuh_layer_id        equal to layer_id_in_nuh[j].    -   Otherwise within the CVS pictures with nuh_layer_id equal to        layer_id_in_nuh[i and TemporalId greater than        max_tid_il_ref_pics_plus1[i] [j −1 are not used as reference for        inter-layer prediction for pictures with nuh_layer_id equal to        layer_id_in_nuh[j].

When not present, max_tid_il_ref_pics_plus1[i] [j] may be inferred to beequal to 7.

Semantics of all_ref_layers_active_flag is modified.

The modification includes the use of external base layer as specialcase. Thus the value of vps_base_layer_external_flag is utilized todetermine if all the direct reference layers of a layer are used toobtain reference pictures for inter-layer prediction for a currentpicture.

all_ref_layers_active_flag equal to 1 may specify that for each picturereferring to the VPS, the reference layer pictures that belong to alldirect reference layers of the layer containing the picture and thatmight be used for inter-layer prediction as specified by the values ofvps_base_layer_external_flag, sub_layers_vps_max_minus1[i] andmax_tid_il_ref_pics_plus1[i] [j] are present in the same access unit asthe picture and are included in the inter-layer reference picture set ofthe picture. all_ref_layers_active_flag equal to 0 specifies that theabove restriction may or may not apply.

Information regarding reference pictures used for inter-layer predictionfor a current picture maybe signaled in slice segment header of thecurrent picture. An exemplary syntax for this signaling in slice segmentheader is shown in table below.

slice_segment_header( ) { ...    if( sps_temporal_mvp_enabled_flag )    slice_temporal_mvp_enabled_flag u(1)   }   if( nuh_layer_id > 0 &&!all_ref_layers_active_flag &&       NumDirectRefLayers[ nuh_layer_id] > 0 ) {    inter_layer_pred_enabled_flag u(1)    if(inter_layer_pred_enabled_flag &&    NumDirectRefLayers[ nuh_layer_id] > 1) {     if( !max_one_active_ref_layer_flag )     num_inter_layer_ref_pics_minus1 u(v)     if( NumActiveRefLayerPics!=     NumDirectRefLayers[ nuh_layer_id ] )      for( i = 0; i <NumActiveRefLayerPics; i++ )       inter_layer_pred_layer_idc[ i ] u(v)   }   } ... }

Semantics of num_inter_layer_ref_pics_minus1 is modified with respect tothe derivation of refLayerPicIdc when a direct reference layer isexternally specified base layer.

Since a TemporalId is not associated with externally specified baselayer the checks related to comparing the TemporalId value of externallyspecified base layer picture with sub_layers_vps_max_minus1[refLayerIdx] and max_tid_il_ref_pics_plus1[refLayerIdx][LayerIdxInVps[nuh_layer_id]] is omitted and the picture is added torefLayerPicIdc, numActiveRefLayerPics derivation and subsequentlyNumActiveRefLayerPics derivation when all ref layers active flag is 1.

‘inter_layer_pred_enabled_flag’ equal to 1 may specify that inter-layerprediction may be used in decoding of the current picture.inter_layer_pred_enabled_flag equal to 0 may specify that inter-layerprediction is not used in decoding of the current picture.

‘num_inter_layer_ref_pics_minus1’ plus 1 may specify the number ofpictures that may be used in decoding of the current picture forinter-layer prediction. The length of thenum_inter_layer_ref_pics_minus1 syntax element isCeil(Log2(NumDirectRefLayers[nuh_layer_id])) bits. The value ofnum_inter_layer_ref_pics_minus1 may be in the range of 0 toNumDirectRefLayers[nuh_layer_id]−1, inclusive.

The variables numRefLayerPics and refLayerPicFlag[i] andrefLayerPicIdc[j] may be derived as follows:

 for( i = 0, j = 0; i < NumDirectRefLayers[ nuh_layer_id ]; i++ ) {   refLayerIdx = LayerIdxInVps[ RefLayerId[ nuh_layer_id ][ i ] ]   if(refLayerIdx == 0 && vps_base_layer_external_flag )     refLayerPicIdc[j++ ] = i   else if( sub_layers_vps_max_minus1[ refLayerIdx ] >=TemporalId && max_tid_il_ref_pics_plus1[ refLayerIdx ] [ LayerIdxInVps[nuh_layer_id ] ] > TemporalId )     refLayerPicIdc[ j++ ] = i  } numRefLayerPics = j The variable NumActiveRefLayerPics may be derivedas follows:  if( nuh_layer_id = = 0 | | NumDirectRefLayers[ nuh_layer_id] = =  0 )   NumActiveRefLayerPics = 0  else if(all_ref_layers_active_flag )   NumActiveRefLayerPics = numRefLayerPics else if( !inter_layer_pred_enabled_flag )   NumActiveRefLayerPics = 0 else if( max_one_active_ref_layer_flag | |  NumDirectRefLayers[nuh_layer_id ] = = 1 )   NumActiveRefLayerPics = 1  else  NumActiveRefLayerPics = num_inter_layer_ref_pics_minus1 + 1 All slicesof a coded picture shall have the same value of NumActiveRefLayerPics.

A condition is added regarding bitstream conformance for each value of iin the range of 0 to NumActiveRefLayerPics−1, inclusive.

The condition regarding relation between TemporalId andmax_tid_il_ref_pics_plus1 is relaxed for externally specified base layerwhich does not have a TemporalId value associated with it.

‘inter_layer_pred_layer_idc’ [i] may specify the variable,RefPicLayerId[i], representing the nuh_layer_id of the i-th picture thatmay be used by the current picture for inter-layer prediction. Thelength of the syntax element inter_layer_pred_layer_idc[ i] isCeil(Log2(NumDirectRefLayers[nuh_layer_id])) bits. The value ofinter_layer_pred_layer_idc[i] shall be in the range of 0 toNumDirectRefLayers[nuh_layer_id]−1, inclusive. When not present, thevalue of inter_layer_pred_layer_idc[i] is inferred to be equal torefLayerPicIdc[i].

When i is greater than 0, inter_layer_pred_layer_idc[i] shall be greaterthan inter_layer_pred_layer_idc[i−1].

The variables RefPicLayerId[i] for all values of i in the range of 0 toNumActiveRefLayerPics−1, inclusive, may be derived as follows:

for( i = 0, j = 0; i < NumActiveRefLayerPics; i ++)    RefPicLayerId[ i] = RefLayerId[ nuh_layer_id ][ inter_layer_pred_layer_idc[ i ] ]

It is a requirement of bitstream conformance that for each value of i inthe range of 0 to NumActiveRefLayerPics−1, inclusive, either of thefollowing conditions shall be true:

vps_base_layer_external_flag is equal to 1 and RefPicLayerId[i] is equalto 0.

   The value of max_tid_il_ref_pics_plus1[ LayerIdxInVps[ RefPicLayerId[i ] ] ] [ LayerIdxInVps[ nuh_layer_id ] ] is greater than TemporalId.   The values of max_tid_il_ref_pics_plus1[ LayerIdxInVps[RefPicLayerId[ i ] ] ] [ LayerIdxInVps[ nuh_layer_id ] ] and TemporalIdare both equal to 0 and the picture in the current access unit withnuh_layer_id equal to RefPicLayerId[ i ] is an IRAP picture.

Thus it is allowed to include in of the NumActiveRefLayerPics andRefPicLayerid[i] which indicate the pictures that may be used asreference pictures for inter-layer prediction for the current picture aexternally specified base layer picture if the externally specified baselayer picture is a direct reference layer for the layer to which thecurrent picture belongs.

A modification is applied to marking process for sub-layer non-referencepictures not needed for inter-layer prediction.

When performing the marking process for sub-layer non-reference picturesnot needed for inter-layer prediction the pictures of externallyspecified base layer are omitted.

The Decoding process for ending the decoding of a coded picture withnuh_layer_id greater than 0 may be as follows:

PicOutputFlag is set as follows:    If LayerInitializedFlag[nuh_layer_id ] is equal to 0, PicOutputFlag is set equal to 0.   Otherwise, if the current picture is a RASL picture andNoRaslOutputFlag of the associated IRAP picture is equal to 1,PicOutputFlag is set equal to 0.    Otherwise, PicOutputFlag is setequal to pic_output_flag.

The following applies:

-   -   If discardable_flag is equal to 1, the decoded picture is marked        as “unused for reference”.    -   Otherwise, the decoded picture is marked as “used for short-term        reference”.

When TemporalId is equal to HighestTid, the marking process forsub-layer non-reference pictures not needed for inter-layer predictionspecified in subclause “Marking process for sub-layer non-referencepictures not needed for inter-layer prediction” below may be invokedwith latestDecLayerId equal to nuh_layer_id as input.

When FirstPicInLayerDecodedFlag[nuh_layer_id] is equal to 0,FirstPicInLayerDecodedFlag[nuh_layer_id] is set equal to 1.

Marking process for sub-layer non-reference pictures not needed forinter-layer prediction may be as follows:

Input to this process is:    a nuh_layer_id value latestDecLayerIdOutput of this process is:    potentially updated marking as “unused forreference” for some decoded pictures

-   -   This process marks pictures that are not needed for inter or        inter-layer prediction as “unused for reference”. When        TemporalId is less than HighestTid, the current picture may be        used for reference in inter prediction and this process is not        invoked.

The variables numTargetDecLayers, and latestDecIdx are derived asfollows:

  numTargetDecLayers is set equal to the number of entries inTargetDecLayerIdList.   latestDecIdx is set equal to the value of i forwhich TargetDecLayerIdList[ i ] is equal to latestDecLayerId.

For i in the range of 0 to latestDecIdx, inclusive, the followingapplies for marking of pictures as “unused for reference”:

 Let currPic be the picture in the current access unit with nuh_layer_id equal to TargetDecLayerIdList[ i ].  When currPic is marked as “usedfor reference”, is a sub-layer non-  reference picture andvps_base_layer_external_flag is equal  to 0 orvps_base_layer_external_flag is equal to 1 and  TargetDecLayerIdList[ i] is not equal to 0, the following applies:   The variable currTid isset equal to the value of TemporalId of   currPic.   The variableremainingInterLayerReferencesFlag is derived as   specified in thefollowing:   remainingInterLayerReferencesFlag = 0   iLidx =LayerIdxInVps[ TargetDecLayerIdList[ i ] ]    for( j = latestDecIdx + 1;j < numTargetDecLayers; j++ ) {     jLidx = LayerIdxInVps[TargetDecLayerIdList[ j ] ]     if( currTid <= (max_tid_il_ref_pics_plus1[ iLidx ]     [ jLidx ] − 1 ) )      for( k =0; k < NumDirectRefLayers [ TargetDecLayerIdList[ j ] ]; k++ )       if(TargetDecLayerIdList[ i ] = = RefLayerId[ TargetDecLayerIdList[ j ] ][ k] )        remainingInterLayerReferencesFlag = 1   }  WhenremainingInterLayerReferenceFlag is equal to 0, currPic is  marked as“unused for reference”.

In another embodiment following change may be made to the “Markingprocess for sub-layer non-reference pictures not needed for inter-layerprediction”.

Input to this process is:  a nuh_layer_id value latestDecLayerId Outputof this process is:  potentially updated marking as “unused forreference” for some decoded  pictures  This process marks pictures thatare not needed for inter or inter-layer  prediction as “unused forreference”. When TemporalId is less than  HighestTid, the currentpicture may be used for reference in inter prediction  and this processis not invoked. The variables numTargetDecLayers, and latestDecIdx arederived as follows:  numTargetDecLayers is set equal to the number ofentries in  TargetDecLayerIdList.  latestDecIdx is set equal to thevalue of i for which TargetDecLayerIdList[ i ] is  equal tolatestDecLayerId. For i in the range of 0 to latestDecIdx, inclusive,the following applies for marking   of pictures as “unused forreference”:   Let currPic be the picture in the current access unit withnuh_layer_id equal   to TargetDecLayerIdList[ i ].   When currPic ismarked as “used for reference” , is a sub-layer non-    referencepicture the following applies:    The variable currTid is set equal tothe value of TemporalId of currPic.    The variableremainingInterLayerReferencesFlag is derived as specified    in thefollowing:   remainingInterLayerReferencesFlag = 0   if(vps_base_layer_external_flag == 1 && (TargetDecLayerIdList[ i ] == 0) ){      remainingInterLayerReferencesFlag = 1 } else {    iLidx =LayerIdxInVps[ TargetDecLayerIdList[ i ] ]     for( j = latestDecIdx +1; j < numTargetDecLayers; j++ ) {      jLidx = LayerIdxInVps[TargetDecLayerIdList[ j ] ]      if( currTid <= (max_tid_il_ref_pics_plus1[ iLidx ][ jLidx ] − 1 ) )       for( k = 0; k< NumDirectRefLayers[ TargetDecLayerIdList[ j ] ]; k++ )        if(TargetDecLayerIdList[ i ] = = RefLayerId[ TargetDecLayerIdList[ j ] ][ k] )         remainingInterLayerReferencesFlag = 1     } }    WhenremainingInterLayerReferenceFlag is equal to 0, currPic is marked    as“unused for reference”.

In another embodiment following change may be made to the “Markingprocess for sub-layer non-reference pictures not needed for inter-layerprediction”.

Input to this process is:  a nuh_layer_id value latestDecLayerId Outputof this process is:  potentially updated marking as “unused forreference” for some decoded  pictures  This process marks pictures thatare not needed for inter or inter-layer  prediction as “unused forreference”. When TemporalId is less than  HighestTid, the currentpicture may be used for reference in inter prediction  and this processis not invoked. The variables numTargetDecLayers, and latestDecIdx arederived as follows:  numTargetDecLayers is set equal to the number ofentries in  TargetDecLayerIdList.  latestDecIdx is set equal to thevalue of i for which TargetDecLayerIdList[ i ] is  equal tolatestDecLayerId. For i in the range of vps_base_layer_external_flag? 1:0 to latestDecIdx, inclusive, the following applies for marking ofpictures as “unused for reference”:   Let currPic be the picture in thecurrent access unit with nuh_layer_id equal   to TargetDecLayerIdList[ i].   When currPic is marked as “used for reference” , is a sub-layernon-   reference picture the following applies:    The variable currTidis set equal to the value of TemporalId of currPic.    The variableremainingInterLayerReferencesFlag is derived as specified    in thefollowing:   remainingInterLayerReferencesFlag = 0    iLidx =LayerIdxInVps[ TargetDecLayerIdList[ i ] ]     for( j = latestDecIdx +1; j < numTargetDecLayers; j++ ) {      jLidx = LayerIdxInVps[TargetDecLayerIdList[ j ] ]      if( currTid <= (max_tid_il_ref_pics_plus1[ iLidx ][ jLidx ] − 1 ) )       for( k = 0; k< NumDirectRefLayers[ TargetDecLayerIdList[ j ] ]; k++ )        if(TargetDecLayerIdList[ i ] = = RefLayerId[ TargetDecLayerIdList[ j ] ][ k] )         remainingInterLayerReferencesFlag = 1     }    WhenremainingInterLayerReferenceFlag is equal to 0, currPic is marked    as“unused for reference”.

In another embodiment following change may be made to the “Markingprocess for sub-layer non-reference pictures not needed for inter-layerprediction”.

Input to this process is:  a nuh_layer_id value latestDecLayerId Outputof this process is:  potentially updated marking as “unused forreference” for some decoded  pictures  This process marks pictures thatare not needed for inter or inter-layer  prediction as “unused forreference”. When TemporalId is less than  HighestTid, the currentpicture may be used for reference in inter prediction  and this processis not invoked. The variables numTargetDecLayers, and latestDecIdx arederived as follows:  numTargetDecLayers is set equal to the number ofentries in  TargetDecLayerIdList.  latestDecIdx is set equal to thevalue of i for which TargetDecLayerIdList[ i ] is  equal tolatestDecLayerId. For i in the range of 0 to latestDecIdx, inclusive,the following applies for marking of pictures as “unused for reference”:  Let currPic be the picture in the current access unit withnuh_layer_id equal   to TargetDecLayerIdList[ i ].   When currPic ismarked as “used for reference” , is a sub-layer non-   reference picturethe following applies:    The variable currTid is set equal to the valueof TemporalId of currPic.    The variableremainingInterLayerReferencesFlag is derived as specified    in thefollowing:    remainingInterLayerReferencesFlag = 0    iLidx =LayerIdxInVps[ TargetDecLayerIdList[ i ] ]     for( j = latestDecIdx +1; j < numTargetDecLayers; j++ ) {      jLidx = LayerIdxInVps[TargetDecLayerIdList[ j ] ]      if( (currTid <= (max_tid_il_ref_pics_plus1[ iLidx ][ jLidx ] − 1 ) ) ||(vps_base_layer_external_flag==1 && (TargetDecLayerIdList[ i ] == 0) ) )      for( k = 0; k < NumDirectRefLayers[ TargetDecLayerIdList[ j ] ];k++ )        if( TargetDecLayerIdList[ i ] = = RefLayerId[TargetDecLayerIdList[ j ] ][ k ] )        remainingInterLayerReferencesFlag = 1     }  WhenremainingInterLayerReferenceFlag is equal to 0, currPic is marked as “unused for reference”.

Additionally following change modifications are applied to thesub-bitstream property SEI message with respect to the sub-bitstreamextraction process when base layer is externally specified Sub-bitstreamproperty SEI message semantics.

] An exemplary sub-bitstream property SEI message syntax is shown below.

sub_bitstream_property( payloadSize ) { Descriptor  active_vps_id u(4) num_additional_sub_streams_minus1 ue(v)  for( i = 0; i <=num_additional_sub_streams_minus1;  i++) {   sub_bitstream_mode[ i ]u(2)   output_layer_set_idx_to_vps[ i ] ue(v)   highest_sublayer_id[ i ]u(3)   avg_bit_rate[ i ] u(16)   max_bit_rate[ i ] u(16)  } }

The proposed modifications exclude removal of NAL units corresponding toan externally specified base layer during sub0bitstream extractionprocess.

The sub-bitstream property SEI message, when present, provides the bitrate information for a sub-bitstream created by discarding thosepictures in the layers that do not belong to the output layers of theoutput layer sets specified by the active VPS and that do not affect thedecoding of the output layers.

When present, the sub-bitstream property SEI message shall be associatedwith an initial IRAP access unit, and the information provided by theSEI messages applies to the bitstream corresponding to the CVScontaining the associated initial IRAP access unit.

‘active_vps_id’ may identify the active VPS. The value of active vps idshall be equal to the value of vps video parameter set id of the activeVPS referred to by the VCL NAL units of the associated access unit.

‘num_additional_sub_streams_minus1’ plus 1 may specify the number of thesub-bitstreams for which the bit rate information may be provided bythis SEI message. The value of num additional sub streams minus1 shallbe in the range of 0 to 2¹⁰−1, inclusive.

‘sub_bitstream_mode[i]’ may specify how the i-th sub-bitstream isgenerated. The value of sub_bitstream_mode[i] shall be equal to 0 or 1,inclusive. The values 2 and 3 are reserved for future use by ITU-T andISO/IEC. When sub_bitstream_mode[i] is the greater than 1, decodersshall ignore the syntax elements output_layer_set_idx_to_vps[i],highest_sublayer_id[i], avg_bit_rate[i], and max_bit_rate[i].

When sub_bitstream_mode[i] is equal to 0, the i-th sub-bitstream isgenerated may be specified by the following steps:

-   -   The sub-bitstream extraction process as specified in clause 10        is invoked with the bitstream corresponding to the CVS        containing the sub-bitstream property SEI message,        highest_sublayer_id[i], and        LayerSetLayerIdList[LayerSetIdxForOutputLayerSet[output_layer_set_idx_to_v        ps[i]]] as inputs.

Remove all NAL units for which the nuh_layer_id is not included inTargetOptLayerIdList and either of the following conditions is true:

   The value of nal_unit_type is not in the range of BLA_W_LP toRSV_IRAP_VCL23, inclusive, and max_tid_il_ref_pics_plus1[ LayerIdxInVps[nuh_layer_id ] ]  [LayerIdxInVps[ layerId ] ] is equal to 0 for layerIdvalues included in  TargetOptLayerIdList.   vps_base_layer_external_flag is equal to 0 orvps_base_layer_external_flag is equal to 1 and nuh_layer_id is not equalto 0 and TemporalId is greater than the maximum value ofmax_tid_il_ref_pics_plus1[ LayerIdxInVps[ nuh_layer_id ] ] [LayerIdxInVps[ layerId ] ] − 1 for all layerId values included in TargetOptLayerIdList.

When sub_bitstream_mode[i] is equal to 1, the i-th sub-bitstream isgenerated as specified by the above steps followed by:

Remove all NAL units with nuh_layer_id not among the values included inTargetOptLayerIdList and with discardable flag equal to 1.

‘output_layer_set_idx_to_vps[i]’ may specify the index of the outputlayer set corresponding to the i-th sub-bitstream.

‘highest_sublayer_id’ [i] may specify the highest TemporalId of accessunits in the i-th sub-bitstream when vps_base_layer_external_flag is notequal to 1.

‘avg_bit_rate’ [i] may indicate the average bit rate of the i-thsub-bitstream, in bits per second. The value is given byBitRateBPS(avg_bit_rate[i]) with the function BitRateBPS( ) beingspecified as follows:

BitRateBPS(x)=(x&(2¹⁴−1))*10^((2+(x>>14)))

The average bit rate is derived according to the access unit removaltime specified in clause F.13 of JCTVC-P1008. In the following, bTotalis the number of bits in all NAL units of the i-th sub-bitstream, t₁ isthe removal time (in seconds) of the first access unit to which the VPSapplies, and t₂ is the removal time (in seconds) of the last access unit(in decoding order) to which the VPS applies. With x specifying thevalue of avg_bit_rate[i], the following applies:

-   -   If t₁ is not equal to t₂, the following condition shall be true:

(x&(2¹⁴−1))==Round(bTotal((t ₂ −t ₁)*10^((2+(x>>14)))))

Otherwise (t₁ is equal to t₂), the following condition shall be true:

(x&(2¹⁴−1))==0

max_bit_rate[i] may indicate an upper bound for the bit rate of the i-thsub-bitstream in any one-second time window of access unit removal timeas specified in clause F.13 of JCTVC-P1008. The upper bound for the bitrate in bits per second is given by BitRateBPS(max_bit_rate[i]). The bitrate values are derived according to the access unit removal timespecified in clause F.13. In the following, t₁ is any point in time (inseconds), t₂ is set equal to

t ₁+1÷100,

and bTotal is the number of bits in all NAL units of access units with aremoval time greater than or equal to t₁ and less than t₂. With xspecifying the value of max_bit_rate[i], the following condition shallbe obeyed for all values of t₁:

(x&(2¹⁴−1))>=bTotal((t ₂ −t ₁)*10^((2+(x>>14))))

Semantic information related to the hypothetical reference decoder maylikewise be included in a syntax, such as hrd_layer_set_idx[i]. Withboth internally and externally referenced base layers, it is desirableto be able to determine whether the data in the syntax structure for thebase layer, hrd_layer_set_idx[i]=0, is data related to a particular baselayer or is otherwise filler data having no particular relevance that isignored by the hypothetical reference decoder during the decodingprocess. Therefore, For the case where base layer is not externallyspecified (i.e. is internally specified) a range of values forhrd_layer_set_idx[i] is specified such that the index can point to onlyone of the layers sets in VPS. For the case of externally specified baselayer hrd_layer_set_idx is further restricted from taking a value of 0.By restricting the hrd_layer_set_idx[i] index this way, only HRDparameters that point to one of the potentially available layer sets arepermitted, and whether the base layer is included depends on whether itis an externally specified base layer.

The hrd_layer_set_idx[i] specifies the index, into the list of layersets specified by the VPS, of the layer set to which the i thhrd_parameters( ) syntax structure in the VPS applies. In conformingbitstreams, the value of hrd_layer_set_idx[i] shall be in the range of(vps_base_layer_external_flag?1: 0) to vps_num_layer_sets_minus1,inclusive.

Additional constraints may be included to avoid signaling duplicatehrd_parameters( ) for a layer set. One additional constraint is arequirement of bitstream conformance that the value ofhrd_layer_set_idx[i] shall not be equal to the value ofhrd_layer_set_idx[j] for any value of j not equal to i. Anotherconstraint may be on vps_num_layer_sets_minus1 syntax element.vps_num_layer_sets_minus1 plus 1 specifies the number of layer sets thatare specified by the VPS. The value of vps_num_layer_sets_minus1 shallbe in the range of 0 to 1023, inclusive. Another constraint may be onvps_num_hrd_parameters syntax element. vps_num_hrd_parameters specifiesthe number of hrd_parameters( ) syntax structures present in the VPSRBSP. The value of vps_num_hrd_parameters shall be less than or equal tovps_num_layer_sets_minus1+1, inclusive.

The hrd_parameters( ) syntax structure provides HRD parameters used inthe HRD operations for a layer set. When the hrd_parameters( ) syntaxstructure is included in a VPS, the applicable layer set to which thehrd_parameters( ) syntax structure applies is specified by thecorresponding hrd_layer_set_idx[i] syntax element in the VPS. When thehrd_parameters( ) syntax structure is included in an SPS, the layer setto which the hrd_parameters( ) syntax structure applies is the layer setfor which the associated layer identifier list contains all nuh_layer_idvalues present in the CVS.

Each HEVC, SHVC, MV-HEVC bitstream includes a profile informationregarding what the bitstream conforms to, such as a Main profile thatsupports 8 bits, a Main10 profile that supports 10 bits, and a MainStill Picture profile. Each of the profiles includes one of a pluralityof tiers that define restrictions and/or characteristics of thebitstream, and each tier includes one of a plurality of levels thatprovide further restrictions and/or characteristics of the bitstream.Thus for HEVC, SHVC, MV-HEVC bitstreams a profile_tier_level( )information is signaled which describes the information regardingprofile, tier, level that the bitstream conforms to. An exemplarysignaling scheme may be as shown in the table below.

vps_extension( ) { Descriptor  ... u(1) vps_num_profile_tier_level_minus1 ue(v)  for( ptlIdx = 1; ptlIdx <=vps_num_profile_tier_level_minus1; ptlIdx ++ ) {  vps_profile_present_flag[ ptlIdx ] u(1)   profile_tier_level(vps_profile_present_flag[ ptlIdx ], vps_max_sub_layers_minus1 )  } num_add_output_layer_sets ue(v)  NumOutputLayerSets =num_add_output_layer_sets + vps_num_layer_sets_minus1 + 1  if(NumOutputLayerSets > 1 )   default_target_output_layer_idc u(2)  for( i= 1; i < NumOutputLayerSets; i++ ) {   if( i > vps_num_layer_sets_minus1)    output_layer_set_idx_minus1[ i ] u(v)   if( i >vps_num_layer_sets_minus1 || default_target_output_layer_idc = = 2 )   for( j = 0; j < NumLayersInIdList[ LayerSetIdxForOutputLayerSet[ i ]]; j++)     output_layer_flag[ i ][ j ] u(1)   profile_level_tier_idx[ i] u(v)   if( NumOutputLayersInOutputLayerSet[ i ] = = 1    &&NumDirectRefLayers[ OlsHighestOutputLayerId[ i ] ] > 0 )   alt_output_layer_flag[ i ] u(1)  }  ...   }

The profile_tier_level( ) syntax structure provides profile, tier andlevel information used for a layer set. When the profile_tier_level( )syntax structure is included in a vps_extension( ) syntax structure, theapplicable layer set to which the profile_tier_level( ) syntax structureapplies is specified by the corresponding IsIdx variable in thevps_extension( ) syntax structure. When the profile_tier_level( ) syntaxstructure is included in a VPS, but not in a vps_extension( ) syntaxstructure, the applicable layer set to which the profile_tier_level( )syntax structure applies is the layer set specified by the index 0. Whenthe profile_tier_level( ) syntax structure is included in an SPS, thelayer set to which the profile_tier_level( ) syntax structure applies isthe layer set specified by the index 0.

‘vps_num_profile_tier_level_minus1’ plus 1 specifies the number ofprofile_tier_level( ) syntax structures in the VPS. The value ofvps_num_profile_tier_level minus1 shall be in the range of 0 to 63,inclusive.

The indexing of the profile tier level structure should be based uponwhether the base layer is externally specified. When base layer isexternally specified all bits in the first profile_tier_level( ) syntaxstructure are required to be equal to 0. Thus for i in the range of 1 toNumOutputLayerSets−1, inclusive the profile_level_tier_idx[i] should notpoint to this all zero profile_tier_level( ) structure when base layeris externally specified.

To accommodate the modification to the profile_level_tier_idx[i] it mayspecify the index, into the list of profile_tier_level( ) syntaxstructures in the VPS, of the profile_tier_level( ) syntax structurethat applies to i-th output layer set. The length of theprofile_level_tier idx[i] syntax element isCeil(Log2(vps_num_profile_tier_level_minus1+1)) bits. The value ofprofile_level tier idx[0] is inferred to be equal to 0. The value ofprofile level tier idx[i] for i in the range of 1 toNumOutputLayerSet−1, inclusive shall be in the range of(vps_base_layer_external_flag?1: 0) tovps_num_profile_tier_level_minus1, inclusive.

It is likewise desirable to signal by external means the value of avariable BlRepFormatIdx (e.g., base layer representation format index)which specifies an index into the list of rep_format( ) syntaxstructures in the VPS of the rep_format( ) structure that applies to thedecoded picture with nuh_layer_id equal to 0 specified by externalmeans. This is desirable because otherwise when any of therepresentation format information for the externally specified layerwith nuh_layer_id equal to 0 changes (e.g. change in exterrnallyspecified base layer picture height or width), a new VPS will need to beactivated since currently the 0'th representation format structure isalways selected to indicate representation format of the base layer Theadditional VPS would result in a substantial increase in the bits of thebitstream, and also undue computational complexity.

The semantics of the decoding process may be as follows, which includesaccommodations for the BlRepFormatIdx and the externally referenced baselayer:

-   -   When vps_base_layer_external_flag is equal to 1, the following        applies:        -   There is no coded picture with nuh_layer_id equal to 0 in            the bitstream.        -   The size of the sub-DPB for the layer with nuh_layer_id            equal to 0 is set equal to 1.        -   In addition to a list of decoded pictures, this process also            outputs a flag BaseLayerOutputFlag, and, when            BaseLayerOutputFlag is equal to 0 and            AltOptLayerFlag[TargetOptLayerSetIdx] is equal to 1, a flag            BaseLayerPicOutputFlag for each access unit.            -   The BaseLayerOutputFlag and, when present,                BaseLayerPicOutputFlag for each access unit, are to be                sent by an external means to the base layer decoder for                controlling the output of base layer decoded pictures.    -   The following applies:        -   BaseLayerOutputFlag is derived as follows:            -   BaseLayerOutputFlag=(TargetOptLayerIdList[0]==0)        -   BaseLayerOutputFlag equal to 1 specifies that the base layer            is a target output layer.        -   BaseLayerOutputFlag equal to 0 specifies that the base layer            is a not target output layer.    -   When BaseLayerOutputFlag is equal to 0 and        AltOptLayerFlag[TargetOptLayerSetIdx ] is equal to 1, for each        access unit, BaseLayerPicOutputFlag is derived as follows:        -   if(the base layer is a direct or indirect reference layer of            the target output layer, the access unit does not contain a            picture at the target output layer and does not contain a            picture at any other direct or indirect reference layer of            the target output layer)            -   BaseLayerPicOutputFlag=1        -   else            -   BaseLayerPicOutputFlag=0    -   BaseLayerPicOutputFlag equal to 1 for an access unit specifies        that the base layer picture of the access unit is output.        BaseLayerPicOutputFlag equal to 0 for an access unit specifies        that the base layer picture of the access unit is not output.    -   For each access unit, a decoded picture with nuh_layer_id equal        to 0 may be provided by external means. When not provided, no        picture with nuh_layer_id equal to 0 is used for inter-layer        prediction for the current access unit. When provided, the        following applies:        -   The following information of the picture with nuh_layer_id            equal to 0 for the access unit is provided by external            means:            -   The decoded sample values (1 sample array SL if                chroma_format_idc is equal to 0 or 3 sample arrays SL,                SCb, and SCr otherwise)            -   The value of the variable BIRepFormatIdx which specifies                an index into the list of rep_format( ) syntax                structures in the VPS of the rep_format( ) structure                that applies to the decoded picture with nuh_layer_id                equal to 0.                -   The values of pic_width_in_luma_samples,            -   pic_height_in_luma_samples, chroma_format_idc,                separate_colour_plane_flag, bit_depth_luma_minus8, and                bit_depth_chroma_minus8 for decoded pictures with                nuh_layer_id equal to 0 are set equal to the values of                pic_width_vps_in_luma_samples,            -   pic_height_vps_in_luma_samples, chroma_format_vps_idc,                separate_colour_plane_vps_flag,                bit_depth_vps_luma_minus8, and            -   bit_depth_vps_chroma_minus8, respectively, of the                BlRepFormatIdx'th rep_format( ) syntax structure in the                active VPS.            -   The value of the variable BlIrapPicFlag, and when                BlIrapPicFlag is equal to 1, the value of nal_unit_type                of the decoded picture                -   BlIrapPicFlag equal to 1 specifies that the decoded                    picture is an IRAP picture. BlIrapPicFlag equal to 0                    specifies that the decoded picture is a non-I RAP                    picture.                -   The provided value of nal_unit_type of the decoded                    picture shall be equal to IDR_W_RADL, CRA_NUT, or                    BLA_W_LP.                -    nal_unit_type equal to IDR_W_RADL specifies that                    the decoded picture is an IDR picture.                -    nal_unit_type equal to CRA_NUT specifies that the                    decoded picture is a CRA picture.                -    nal_unit_type equal to BLA_W_LP specifies that the                    decoded picture is a BLA picture.        -   The following applies for the decoded picture with            nuh_layer_id equal to 0 for the access unit:            -   The decoded picture with nuh_layer_id equal to 0 is                stored in the sub-DPB for the layer with nuh_layer_id                equal to 0 and is marked as “used for long-term                reference”.            -   If the access unit has at least one picture with                nuh_layer_id greater than 0, the PicOrderCntVal of the                decoded picture with nuh_layer_id equal to 0 is set                equal to the PicOrderCntVal of any picture with                nuh_layer_id greater than 0 in the access unit.                Otherwise, the decoded picture with nuh_layer_id equal                to 0 is discarded and the sub-DPB for the layer with                nuh_layer_id equal to 0 is set to be empty.        -   When the access unit has at least one picture with            nuh_layer_id greater than 0, after all pictures in the            access unit are decoded, the sub-DPB for the layer with            nuh_layer_id equal to 0 is set to be empty.

In another embodiment the following may apply:

The value of the variable BIRepFormatIdx which specifies an index intothe list of rep_format( ) syntax structures in the VPS of therep_format( ) structure that applies to the decoded picture withnuh_layer_id equal to 0.

-   -   -   The values of pic_width_in_luma_samples,            pic_height_in_luma_samples, chroma_format_idc,            separate_colour_plane_flag, bit_depth_luma_minus8, and            bit_depth_chroma_minus8 for decoded pictures with            nuh_layer_id equal to 0 are set equal to the values of pic            width_vps_in_luma_samples, pic_height_vps_in_luma_samples,            chroma_format_vps_idc, separate_colour_plane_vps_flag,            bit_depth_vps_luma_minus8, and bit_depth_vps_chroma_minus8,            respectively, of the vps_rep_format[BIRepFormatIdx] th            rep_format( ) syntax structure in the active VPS.

In another embodiment instead of a single variable BlRepFormatIdx index,a flag BlRepFmtFlag and a variable BlRepFmtIdx may be specified for eachdecoded picture with nuh_layer_id equal to 0 that is specified byexternal means. In this case the following may apply during generaldecoding process.

-   -   For each access unit, a decoded picture with nuh_layer_id equal        to 0 may be provided by external means. When not provided, no        picture with nuh_layer_id equal to 0 is used for inter-layer        prediction for the current access unit. When provided, the        following applies:        -   The following information of the picture with nuh_layer_id            equal to 0 for the access unit is provided by external            means:            -   The decoded sample values (1 sample array SL if                chroma_format_idc is equal to 0 or 3 sample arrays SL,                SCb, and SCr otherwise)            -   The value of the variable BIRepFmtFlag, and when                BIRepFmtFlag is equal to 1, the value of the variable                BIRepFmtIdx which specifies an index into the list of                rep_format( ) syntax structures in the VPS of the                rep_format( ) structure that applies to the decoded                picture with nuh_layer_id equal to 0.                -   The values of pic_width_in_luma_samples,                    pic_height_in_luma_samples, chroma_format_idc,                    separate_colour_plane_flag, bit_depth_luma_minus8,                    and bit_depth_chroma_minus8 for decoded pictures                    with nuh_layer_id equal to 0 are set equal to the                    values of pic_width_vps_in_luma_samples,                    pic_height_vps_in_luma_samples,                    chroma_format_vps_idc,                    separate_colour_plane_vps_flag,                    bit_depth_vps_luma_minus8, and                    bit_depth_vps_chroma_minus8, respectively, of the                    vps_rep_format[0] th rep_format( ) syntax structure                    if BIRepFmtFlag is equal to 0 or BIRepFmtIdx th                    rep_format( ) syntax structure if BIRepFmtFlag is                    equal to 1 in the active VPS.            -   The value of the variable BlIrapPicFlag, and when                BlIrapPicFlag is equal to 1, the value of nal_unit_type                of the decoded picture                -   BlIrapPicFlag equal to 1 specifies that the decoded                    picture is an IRAP picture. BlIrapPicFlag equal to 0                    specifies that the decoded picture is a non-IRAP                    picture.                -   The provided value of nal_unit_type of the decoded                    picture shall be equal to IDR_W_RADL, CRA_NUT, or                    BLA_W_LP.                -    nal_unit_type equal to IDR_W_RADL specifies that                    the decoded picture is an IDR picture.                -    nal_unit_type equal to CRA_NUT specifies that the                    decoded picture is a CRA picture.                -    nal_unit_type equal to BLA_W_LP specifies that the                    decoded picture is a BLA picture.        -   The following applies for the decoded picture with            nuh_layer_id equal to 0 for the access unit:            -   The decoded picture with nuh_layer_id equal to 0 is                stored in the sub-DPB for the layer with nuh_layer_id                equal to 0 and is marked as “used for long-term                reference”.            -   If the access unit has at least one picture with                nuh_layer_id greater than 0, the PicOrderCntVal of the                decoded picture with nuh_layer_id equal to 0 is set                equal to the PicOrderCntVal of any picture with                nuh_layer_id greater than 0 in the access unit.                Otherwise, the decoded picture with nuh_layer_id equal                to 0 is discarded and the sub-DPB for the layer with                nuh_layer_id equal to 0 is set to be empty.        -   When the access unit has at least one picture with            nuh_layer_id greater than 0, after all pictures in the            access unit are decoded, the sub-DPB for the layer with            nuh_layer_id equal to 0 is set to be empty.

In another embodiment the following may apply:

-   -   The value of the variable BIRepFmtFlag, and when BIRepFmtFlag is        equal to 1, the value of the variable BIRepFmtIdx which        specifies an index into the list of rep_format( ) syntax        structures in the VPS of the rep_format( ) structure that        applies to the decoded picture with nuh_layer_id equal to 0.        -   The values of pic_width_in_luma_samples,            pic_height_in_luma_samples, chroma_format_idc,            separate_colour plane_flag, bit_depth_luma_minus8, and            bit_depth_chroma_minus8 for decoded pictures with            nuh_layer_id equal to 0 are set equal to the values of            pic_width_vps_in_luma_samples,            pic_height_vps_in_luma_samples, chroma_format_vps_idc,            separate_colour_plane_vps_flag, bit_depth_vps_luma_minus8,            and bit_depth_vps_chroma_minus8, respectively, of the            vps_rep_format[0] th rep_format( ) syntax structure if            BIRepFmtFlag is equal to 0 or vps_rep_format[BIRepFmtIdx] th            rep_format( ) syntax structure if BIRepFmtFlag is equal to 1            in the active VPS.

In another embodiment some of the above described embodiments may becombined.

In particular the derivation of TemporalId values and derivation ofrepresentation format for the base layer picture externally specifiedmay be combined. In one embodiment this may be done as follows.

The semantics of the decoding process may be as follows, which includesaccommodations for the BlRepFormatIdx and the externally referenced baselayer:

-   -   When vps_base_layer_external_flag is equal to 1, the following        applies:        -   There is no coded picture with nuh_layer_id equal to 0 in            the bitstream.        -   The size of the sub-DPB for the layer with nuh_layer_id            equal to 0 is set equal to 1.        -   In addition to a list of decoded pictures, this process also            outputs a flag BaseLayerOutputFlag, and, when            BaseLayerOutputFlag is equal to 0 and            AltOptLayerFlag[TargetOptLayerSetIdx] is equal to 1, a flag            BaseLayerPicOutputFlag for each access unit.            -   The BaseLayerOutputFlag and, when present,                BaseLayerPicOutputFlag for each access unit, are to be                sent by an external means to the base layer decoder for                controlling the output of base layer decoded pictures.    -   The following applies:        -   BaseLayerOutputFlag is derived as follows:            -   BaseLayerOutputFlag=(TargetOptLayerIdList[0]==0)        -   BaseLayerOutputFlag equal to 1 specifies that the base layer            is a target output layer.        -   BaseLayerOutputFlag equal to 0 specifies that the base layer            is a not target output layer.    -   When BaseLayerOutputFlag is equal to 0 and        AltOptLayerFlag[TargetOptLayerSetIdx ] is equal to 1, for each        access unit, BaseLayerPicOutputFlag is derived as follows:        -   if(the base layer is a direct or indirect reference layer of            the target output layer, the access unit does not contain a            picture at the target output layer and does not contain a            picture at any other direct or indirect reference layer of            the target output layer)            -   BaseLayerPicOutputFlag=1        -   else            -   BaseLayerPicOutputFlag=0    -   BaseLayerPicOutputFlag equal to 1 for an access unit specifies        that the base layer picture of the access unit is output.        BaseLayerPicOutputFlag equal to 0 for an access unit specifies        that the base layer picture of the access unit is not output.    -   For each access unit, a decoded picture with nuh_layer_id equal        to 0 may be provided by external means. When not provided, no        picture with nuh_layer_id equal to 0 is used for inter-layer        prediction for the current access unit. When provided, the        following applies:        -   The following information of the picture with nuh_layer_id            equal to 0 for the access unit is provided by external            means:            -   The decoded sample values (1 sample array SL if                chroma_format_idc is equal to 0 or 3 sample arrays SL,                SCb, and SCr otherwise)            -   The value of the variable BIRepFormatIdx which specifies                an index into the list of rep_format( ) syntax                structures in the VPS of the rep_format( ) structure                that applies to the decoded picture with nuh_layer_id                equal to 0.                -   The values of pic_width_in_luma_samples,                    pic_height_in_luma_samples, chroma_format_idc,                    separate_colour_plane_flag, bit_depth_luma_minus8,                    and bit_depth_chroma_minus8 for decoded pictures                    with nuh_layer_id equal to 0 are set equal to the                    values of pic_width_vps_in_luma_samples,                    pic_height_vps_in_luma_samples,                    chroma_format_vps_idc,                    separate_colour_plane_vps_flag,                    bit_depth_vps_luma_minus8, and                    bit_depth_vps_chroma_minus8, respectively, of the                    BIRepFormatIdx'th rep_format( ) syntax structure in                    the active VPS.            -   The value of the variable BlIrapPicFlag, and when                BlIrapPicFlag is equal to 1, the value of nal_unit_type                of the decoded picture                -   BlIrapPicFlag equal to 1 specifies that the decoded                    picture is an IRAP picture. BlIrapPicFlag equal to 0                    specifies that the decoded picture is a non-IRAP                    picture.                -   The provided value of nal_unit_type of the decoded                    picture shall be equal to IDR_W_RADL, CRA_NUT, or                    BLA_W_LP.                -    nal_unit_type equal to IDR_W_RADL specifies that                    the decoded picture is an IDR picture.                -    nal_unit_type equal to CRA_NUT specifies that the                    decoded picture is a CRA picture.                -    nal_unit_type equal to BLA_W_LP specifies that the                    decoded picture is a BLA picture.        -   The following applies for the decoded picture with            nuh_layer_id equal to 0 for the access unit:            -   The decoded picture with nuh_layer_id equal to 0 is                stored in the sub-DPB for the layer with nuh_layer_id                equal to 0 and is marked as “used for long-term                reference”.            -   If the access unit has at least one picture with                nuh_layer_id greater than 0, the PicOrderCntVal of the                decoded picture with nuh_layer_id equal to 0 is set                equal to the PicOrderCntVal of any picture with                nuh_layer_id greater than 0 in the access unit.                Otherwise, the decoded picture with nuh_layer_id equal                to 0 is discarded and the sub-DPB for the layer with                nuh_layer_id equal to 0 is set to be empty.            -   In one embodiment, if the access unit has at least one                picture with nuh_layer_id greater than 0, TemporalId of                the decoded picture with nuh_layer_id equal to 0 is set                equal to the TemporalId of any picture with nuh_layer_id                greater than 0 in the access unit.            -   In another embodiment, if BlIrapPicFlag is equal to 1                the TemporalId of the decoded picture with nuh_layer_id                equal to 0 is set equal to 0. Otherwise (if                BlIrapPicFlag is equal to 0) if the access unit has at                least one picture with nuh_layer_id greater than 0,                TemporalId of the decoded picture with nuh_layer_id                equal to 0 is set equal to the TemporalId of any picture                with nuh_layer_id greater than 0 in the access unit.        -   When the access unit has at least one picture with            nuh_layer_id greater than 0, after all pictures in the            access unit are decoded, the sub-DPB for the layer with            nuh_layer_id equal to 0 is set to be empty.

In additional embodiments the term “externally specified” may bereplaced by “specified by external means” or any other equivalent termwhich refers to the aspect that information is provided by someoutside/external means.

In additional embodiments the semantics meaning of flag vps base layerexternal flag may instead be inverted and it may be called vps baselayer internal flag. In this case in all or some of the proposed syntax,semantics above the following replacement maybe performed:

   All occurrences of vps_base_layer_external_flag will be replaced by!vps_base_layer_internal_flag.    All occurrences checking the value ofvps_base_layer_external_flag flag equal to 1 will be replaced bychecking the value of vps_base_layer_internal_flag flag equal to 0.   All occurrences checking the value of vps_base_layer_external_flagflag equal to 0 will be replaced by checking the value ofvps_base_layer_internal_flag flag equal to 1.    All occurrences of (vps_base_layer_external_flag ? 1 : 0) maybe replaced by (!vps_base_layer_internal_flag ? 1 : 0) or by (vps_base_layer_internal_flag ? 0 : 1)    All occurrences of if( (vps_base_layer_external_flag == 0 ) || ( ( vps_base_layer_external_flag== 1) && ( layer_id_in_nuh[ LayerIdxInVps[ RefLayerId[ layer_id_in_nuh[i ] [ j ] ] ] ]!= 0 ) ) ) maybe replaced by    Or by if( (!vps_base_layer_internal_flag == 0 ) || ( (!vps_base_layer_internal_flag == 1 ) && ( layer_id_in_nuh[LayerIdxInVps[ RefLayerId[ layer_id_in_nuh[ i ][ j ] ] ] ]!= 0 ) ) )   if( ( vps_base_layer_internal_flag == 1 ) || ( (vps_base_layer_internal_flag == 0 ) && ( layer_id_in_nuh[ LayerIdxInVps[RefLayerId[ layer_id_in_nuh[ i ][ j ] ] ] ]!= 0 ) ) )

It is to be understood that any of the features, whether indicated asshall or necessary, may be omitted as desired. In addition, the featuresmay be combined in different combinations, as desired.

The term “computer-readable medium” refers to any available medium thatcan be accessed by a computer or a processor. The term“computer-readable medium,” as used herein, may denote a computer-and/or processor-readable medium that is non-transitory and tangible. Byway of example, and not limitation, a computer-readable orprocessor-readable medium may comprise RAM, ROM, EEPROM, CD-ROM or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium that can be used to carry or store desiredprogram code in the form of instructions or data structures and that canbe accessed by a computer or processor. Disk and disc, as used herein,includes compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk and Blu-ray (registered trademark) disc wheredisks usually reproduce data magnetically, while discs reproduce dataoptically with lasers.

It should be noted that one or more of the methods described herein maybe implemented in and/or performed using hardware. For example, one ormore of the methods or approaches described herein may be implemented inand/or realized using a chipset, an ASIC, a large-scale integratedcircuit (LSI) or integrated circuit, etc.

Each of the methods disclosed herein comprises one or more steps oractions for achieving the described method. The method steps and/oractions may be interchanged with one another and/or combined into asingle step without departing from the scope of the claims. In otherwords, unless a specific order of steps or actions is required forproper operation of the method that is being described, the order and/oruse of specific steps and/or actions may be modified without departingfrom the scope of the claims.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the systems, methods, and apparatus described herein withoutdeparting from the scope of the claims.

1. A method for decoding a video bitstream comprising the steps of: (a)receiving said video bitstream; (b) receiving a video parameter setcontaining syntax elements that apply to a base layer or at least oneenhancement layer; (c) receiving a flag specifying whether said baselayer is provided by an external means or provided in said videobitstream; (d) decoding said syntax elements applying to said base layerif said flag specifies said base layer is provided in said videobitstream; and (e) decoding said syntax elements applying to said atleast one enhancement layers.
 2. The method of claim 1 wherein saidsyntax elements include bitrate information and picture rateinformation.
 3. A device for decoding a video bitstream comprising thesteps of: a processor, and a memory associated with the processor;wherein the processor executes instructions stored on the memory toperform: (a) receiving said video bitstream; (b) receiving a videoparameter set containing syntax elements that apply to a base layer orat least one enhancement layer; (c) receiving a flag specifying whethersaid base layer is provided by an external means or provided in saidvideo bitstream; (d) decoding said syntax elements applying to said baselayer if said flag specifies said base layer is provided in said videobitstream; and (e) decoding said syntax elements applying to said atleast one enhancement layers.